Hi,
I'm not saying that a character with a moderately high TeFo cannot be effective or fun, just that a true specialist will blow him away within that specialty. This is as it should be, since the latter devoted 4+ virtues to do just that.
I also disagree that Af+Pu is merely an accelerant. Yes, it is an accelerant. But Puissant keeps an Art score 3 pts higher than otherwise, everything else being equal, which it is. So that's 6 pts of casting score or lab total consistently over the course of a career.
As for Affinity with a TeFo, I see 3 phases. Phase 1 is character creation. Here, a character gets a big sendoff that cannot be duplicated some other way. We can call this Spring, because the character, um, springs forward. Phase 2 is summer, because of all the Summae(r) that he reads. This is probably a short phase, since the character already starts with high scores. (In some sagas, summae are not so readily available, btw.) Here, Affinity is purely an accelerant. Phase 3... Autumn? Heck, I can't think of anything suitable, but the season is correct. Tractatuseses are less of a bonanza than summae, but having an Affinity makes them much more worthwhile, since the extra xps are not capped by book quality. Also, the virtuous specialist who places his 2 exposure xps into the TeFo gets 4xp for the season, during which he can invent spells or enchant items within his specialty. This is kind of attractive! High Art scores aren't worth much without an investment in real world applications. This kind of efficiency also works well for adventure xp and for correspondence xp, in sagas that allow this. Higher Arts let a magus learn associated spells faster and/or of greater difficulty; same with enchantments. It helps Penetration and overcoming casting penalties. This yields extra seasons to boost Arts even higher, try for a breakthrough, train an apprentice, earn fame and glory by writing summae on his favorite Arts....
FWIW, if an Affinity isn't good because it is merely an accelerant, Book Learner is also not a very good virtue.
Of course, a non-specialist in a TeFo can also be very effective. Pu+Af in MT yields lab totals only 3 or 4 points higher, but it applies to all lab work, as does Inventive Genius. Book Learner adds +2 to reading, which is less dramatic than an Affinity because it is useless during character creation and typically offers a lower bonus, but works for everything, acceleration the reading of summae and making tractati more attract...ive. Cyclic Magic (seasonal) lets you specialize slightly during your favorite two seasons (2 seasons adventuring or in the lab, 2 seasons or taking care of business). FM, LLSM.... many good things.
But a specialist who starts with Pu+Af in a TeFo, a focus in some subset of that, maybe Deft Form, maybe Strong Parens (more xp to power that Affinity) will leave Gauntlet qualitatively better than a specialist without those virtues, and is likely to slowly widen the gap, except in a saga where summae are awesome and tractati rare.
A sneaky Tytalus who begins play able to punch through your Aegis with his teleport and rifle through your sanctum with no one noticing... a Flambeau who emerges from Gauntlet able to incinerate pesky faeries.... a junior Guernicus who can silently peer into an abbot's mind in his monastery... these characters are qualitatively different from magi who are simply pretty good with ReCo, CrIg and InMe, respectively.
Anyway,
Ken