I'm playing a Spiritmaster character, and as such, have come to the conclusion that something needs to be done clear up the rules for spirits and Hermetic summoning. The guidelines in TM:RE are a significant step-up, but even they have some problems.
Firstly, there's the question of names. By the example of Incantation of Summoning the Dead, possession of the spirit's name counts as an Arcane Connection. From (I think - my books are in storage) RoP:I, True Names are long laborious and each one needs to be learned seperately. I can see how that'd be perhaps true for Demons, but it still gives confusing precedent. How does this extend to other spirits?
Secondly, there's the question of sphere-of-influence. TM:RE suggests the sensible Mentem covers all spirits with intelligence, Animal those with Cunning, Ignem all those which are Fire etc, and Vim anything realm associated. This contradicts the core which requires all summoning spells to be Realm associated. The same likewise applies to wards. It seems sensible to extend this backwards, such that Ward Against Faeries of the Woods becomes Ward Against Creatures of Wood, removing the realm specificity. After all, it does make more sense for Herbam to be better at blocking plant-based entities, physical or intangible, than Vim.
Next, there's the confusion regarding elementals, one of the mainstays of the fantastic wizard's menagerie. Books have labled elementals as either physical or wholly spirit, spirits capable of physical manifestation and, most recently, as mindless beings lacking either Intelligence or Cunning. I can't actually fathom how that last one would work, since how would you differentiate between an earth elemental and, well, a rock with some Terram Vis in it? For myself, I think the word elemental should describe a broad category of beings, covering all of the above. This does, however, lead on to the next issue: Summoning non-Spirits.
There are no guidelines for summoning physical entities to you. The closest are the Corpus guidelines for teleportation. I see no internal confusion in having summoning physical entities being more difficult than appropriating a spirit, but some solid guidelines would be useful. Rego Mentem would allow for a compulsion to come to a certain place to be caused, with perhaps differences in guidelines for instilling curiousity and demanding action. This, however, makes general summons difficult. A Magus has to be able to sense the target in some way, and this makes, for instance, summoning rabbits in an area impossible unless you can already see them. Given that summoning the beasts of the air and land are so much in the scope of wizardry, some useful guidelines are needed. If a large fire is an arcane connection to all fire elementals in the area, it implies that general arcane connections exist. This is a hefty addition to canon; the implications are rather broad. It treads on the toes of Boundary targets. An alternative approach would be to require an additional magnitude for complexity or targetting general things in the area of voice or sight, such as "the nearest boar". It's a slight fudge, but it's probably not game-breaking. Even from a meta-game point of view, such spells will already be very high level so shouldn't overpower things.
Finally, the issue of spell generality appears. IoStD specifies that it only summons ghosts. TM:RE gives an example spell which summons all Ignem spirits. HoH:S gives a Titanoi spell which specificly summons a Spirit of Anger. At what point do things become too broad? Spirits of Emotions or Spirits of Emotion? Elementals for Vim, or just one element? All Mentem Spirits or just Ghosts? From a metagame perspective, making things too broad is obviously undesirable. Likewise so is making things too narrow. It becomes rather silly if your Summon Fire Elemental doesn't summon some fire elementals because they've got different names. "I'm not a Salamander, I'm an Ethereal Fire Drake". From my musings, I'd propose to allow the nonVim forms to be general, with the different types of spirit being reflected in the arcane connections, names and ritual (and game flavour) trappings required. The realm-specific Vim spells should also be general, but require casting requisites, trading versatility for raw power. This also means that to acquire a few, Might 5 spirits is conceptually easy, but more powerful and named servants become the source of stories without requiring 6 months in the lab per spirit just to proliferate a spell-list.
I know that there's hope that RoP:M will fix some of these issues, or at least clear them up, but since they've been percolating in my head, I thought it best to throw them out and see what people think.