Hi,
I suppose I'll soapbox about Hermetic Theurgy. (I know, the post is about Names of Power, yet HT is the central virtue in this section, so bear with me.)
I see it as a very cool idea that doesn't quite come together, for a reason that I think makes sense.
What is it? It's an alternate spellcasting style.
The drawbacks: Spells take longer to cast, one round to cast the spell and another to tell the spirit what to do. The first round can happen earlier, at the cost of increasing the level of the spell. These spells can fail arbitrarily when the SG wants them too if the spirit is otherwise engaged. These spells can fail if the spirit is chased away or dominated by someone else at the scene. These spells can become useless if their associated spirits are destroyed. These spells do not benefit from the caster's Penetration score, or from any improvements to the caster's Arts scores. These spells are not very good for casting on the magus, because the spirit must cast it at range Touch rather than Per, with all the associated drawbacks. These spells are rare because Hermetic Theurges are rare, so a magus who wants spells of this kind probably has to invent them himself. These spells get very little benefit from Mastery; think about it. The magus has to penetrate the spirit's Might in order for the spell to start working. (This isn't so hard, because the magus has an AC to the spirit. But it also means that the magus needs some Penetration, which might otherwise have been dumped.)
The positives: These spells include Flexible Formulaic Magic, though this benefit is less good than it might be, because Per is pretty useless. A single Major Focus in Spirits can cover just about any spell the magus might want to cast in his entire career. Realm Lore adds to Lab Totals. Names of Power can boost lab and casting totals. He can create non-fatiguing divide by two sponts in his favorite areas. That major focus in spirits will also apply to his familiar, whose silver cord adds to all of his casting and lab totals that involve spirits, which might be all of them.
I believe that the negatives crush the positives, unless you're in Wanderer's game and start play with a very, very experienced magus who can invent all his spells at the height of his power. (But in that game, play a Diedne! 
/24232)
Let's put part of a character together. A good Theurge will have Hermetic Theurgy (duh) and a Major Focus in spirits. He'll have a decent magic theory and a realm lore. He might have a Theurgic Familiar, because those are good.
Will he have Names of Power and Invocation? Not really. Developing Names of Power suck up a lot of seasons. They can add to his lab total, and even to his casting totals, but now he has to actually call the names, and spend seasons that he might otherwise spend learning Arts. Worse, improving a casting total in this way helps only a little, since these spells tend to be invented by the caster and are usually easy to cast, and in any case, boosting the casting total has no effect on the spell's penetration. There isn't much synergy between HT and NoP!!
Invocation is even less helpful. It can add to the casting score for any spell, if seasons are sunk into developing Names of Power, and if the time (and potential stress dice) is taken to cast them. This adds to the casting score, which makes it icky for sponters. It has no effect on penetration for theurgy, so why bother?
So, let's take the theurgy example in the book. Gunnar is creating his Pilum of Fire. If he were a normal magus, he'd simply learn this very common spell from lab notes, and would have access to various texts about mastery. Instead, he invents it. We'll give him Int 3, Sta 3, MT 5, Realm Lore 4, Aura 3. We'll also assume he can invent the spell in 2 seasons. Invoke the Spirit of Akkala is level 30, so this magus needs a lab total of 45 to pull this trick. We can deduce that he has Cr 10 and Ig 10; other values might also work, but these work so we'll use em. If he's in the Faerie Aura described, Akkala works as described. Summoning Akkala involves a casting total of 33, before die and Aura. Nifty.
His rival, Rannug, also has Int 3, Sta 3, MT 5 and lives in Aura 3, but has Penetration 4 instead of RL 4. He also has FFM instead of a focus in spirits. He has two more vp to replace HT and Theurgic Familiar, but let's ignore those for now. He learns the ubiquitous PoF from "Ignem for Idiots," a favorite Flambeau stocking stuffer. This takes him one season. He has a season to kill so gets Mastery 1 in this spell while waiting for Gunnar. He tests his pilum on the faeries! Boosting it to Sight, his casting total is 26 + d10, which means he casts without fatigue. He does risk botching, though: Gunnar might have cast his spell before entering the faerie aura. That advantage goes to Gunnar. But if the spell doesn't botch, Rannug achieves better Penetration: 5 + d10 instead of -3.
Noticing this, Gunnar spends another two seasons inventing a lvl 35 spell to Invoke Nissila. This takes him three seasons even including the similarity bonus, but let's call it two just because. He walks into a divine aura and casts it. This time, he risks botching. Things go as described.
Meanwhile, Rannug does stuff for two seasons. Just for fun, let's say he increases his Cr and Ig both to 11, which is reasonable. Now he goes into a Divine Aura where there's a new hedge wizard of the Ancient and Honorable Order of the Spell Test Dummy waiting for him. Rannug's PoF is still lvl 20, and only requires one round to cast. (Advantage: Rannug.) His casting total will be 17 + d10 to reach a 20, versus Gunnar's 26 + d10 to reach a 35. Rannug will probably not lose a fatigue! (Advantage: Rannug.) Rannug also will roll one less botch die than Gunnar should he roll a zero, and has a spell mastery option that I haven't even bothered with. (Advantage: Rannug.) His Penetration, however, will be only 1 + d10. (Advantage: Gunnar.)
Who is better off? Today, Gunnar does have an advantage in Penetatration. But he also spent one more virtue point (let's ignore the familiar, which didn't come into play here). He also has many disadvantages. It was mighty generous of the hedge wizard to do nothing while Gunnar spent two rounds getting Nissila to do its thing! As time goes by, Rannug's Arts will improve and his Penetration will improve. If he likes his PoF, he might master it further, gaining additional flexibility that Gunnar will never attain. Gunnar will sometimes find himself without a spell when Nissila is detained. What if Nissila is killed? Ooops.
Now, there is one kind of theurgist that could become viable, for a player who can convince an SG to let him play it. grin I might do this sometime. The magus is of a weird Ex Misc lineage whose apprentices are taught by a magus who has become a Daimon. One of the spells that the apprentice learns is to invoke the daimon, and his gauntlet involves a familiar pact with the daimon, who was once a magus and who not only knows Arts and Magic Theory but is also a very good teacher.
The apprentice has to dump lots of points into two Arts, for which he has Affinity and Puissance, so that he can bind the Daimon, whose Might is 20, the minimum possible for an Ascended magus. The apprentice also has HT, MF: Spirits and Theurgic Familiar. The Daimon has Arts scores of at least 15 but no more than 20, a high Int, a high Com, Good Teacher, Teaching 10, Magic Theory 10, Parma 10 and a few other, similar Abilities. Note that Int and Com can exceed +5!!!
The newly Gauntleted magus now has an awesome familiar, who cannot be killed and who will teach him everything he knows in a remarkably short time, to the tune of 26 or more xp per season! The familiar also is an awesome lab assistant for inventing spells, and probably knows more than a few himself. Eventually, the magus finds an apprentice--and his familiar will do the teaching, to continue the lineage. When the magus has outgrown his familiar, a possible initiation script might be to give up this familiar, take on a better one and learn how to Ascend...
Surprisingly, Theurgy lacks synergy for Hermetic magi with Summoning and other Goetic Arts.
But we were talking about Invocation.
It's a major virtue that requires a minor virtue. With a lot of work, it can add some minor casting score bonuses. These get bigger toward the end of a magus' career, yet their total is limited by MT, and each individual component will provide lower bonuses as they become wider, since they do not exceed form and material bonuses covering the same scope. This is a major investment!
So, the virtues of this section create a casting style that is mostly worse than normal Hermetic Magic. And maybe that's the way it should be, because if this were better, everyone would want to do it.
I find it interesting that I was able to pretty much recreate Gunnar by giving him a MF: Spirits, get the outcomes described in the book, and then contrast him with a magus of similar value, also getting reasonable outcomes.
Anyway,
Ken