Good morning, RC. As promised, I have coffee up in me, though my eyes are still ruddy sore from last night's game (Ravenloft). Ah, the high wheelin', big pimp life of a gamer. Sittin' up til' 1 am discussion rules and whether or not my chili was any good (evidently it was, because it was freakin' gone before we'd even started playing.) Ah, chili. We hardly knew ye.
To pick up where I left off:
- Subvert Bound Spirit. I would lean more towards an exorcism and abilities to deal with outsiders, but understanding the traditions as I do, I can't say that this is right out as much as it isn't the flavor I would go for. Your mechanics are sound, and I agree that everyone should have everything at their disposal (no specific advantage). I disagree in a ... a flavor sense, if you will, with the idea of subverting a steadfastly loyal companion.
OTOH, what you're effectively casting is "Charm X" where X retains a certain amount of loyalty and can't (as a Charm spell) be commanded to do anything truly crazy. As we both know, Charm is pretty easy to get your mitts on, but your check is more advanced than a normal DC 10 + 1 + Stat. And, you did limit it by keeping the duration short (also big ups on that, assuming the caster lives long enough to care).
You've got 25 levels here; would you consider bringing it down to X/day? Say... 6/12/18/24? This is (or IMO, should be) a major effort, so to reign it a little bit, that would be my first suggestion until I think of something more concrete.
Speak With Spirits: What was your guage for determining the DCs? I can sit here and posit arguments all day - and never tire - as to what should be set where and why, whether it would make more sense to go by a "power" behind the spirit based on age and responsibility (which is more charting, whee!) or that manufactured items are more difficult to communicate with than living ones. Or vice versa. I don't think we'd accomplish much on that string, so "meh." So - why this particular chart?
The power, otherwise, is well balanced and makes sense. This sort of constant augury is important. Out of curiosity, would the Shaman be able to ask questions of his own equipment to see if they picked up on something he missed? Do you have a mechanic for building up familiarity with those spirits outside of the normal Spiritual Companion?
Unbind Spirits: I thought this might come up.
The effects of having a familiar spirit unbound are exactly the same as having a familiar dismissed: Its former master must attempt a DC 15 Fortitude saving throw. Failure means he loses 200 experience points per level in the class that granted the familiar; success reduces the loss to one-half that amount. However, the former master’s experience point total can never go below 0 as the result of a familiar’s unbinding. A good master regains this lost XP when its familiar rebinds itself. Otherwise, an unbound familiar cannot be replaced for a year and day.
As a DM, I would really hesitate to put this kind of power into a PCs hands. I suppose it's because (similarly to the earlier version) I have the idea in my head that some things are inviolate; that's me, as a DM, more than a problem I see with the mechanic. There are spells which are PC accessible which cost people entire levels, or kill them outright, so merely costing them XP is (comparatively) minor, except it can't be healed or recovered except over time, and that haunts me.
I almost think there should be more set up for it, and the power should be harder to execute. Otherwise by level 10 I'd be unbinding everything left and right. AHA. IMO: You may want to consider adding flavor text that the power is used largely in defense of the spirit. Remebering that the shaman isn't terribly concerned with the state of man, but is concerned with the state of man in cooperation with spirits. If the spirit is unhappy, that would be a worthy reason to unbind it.
Also, if a spirit (say, a Paladin's Mount, which should be a nearly unbreakable bond) has no interest in being Unbound, there should definately be some sort of additional attempt on the spirit's part, in association with its master (and other broadcasting companies) to not get severed. The mechanic you have treats the spirit as an object, which can be attached or removed like a LEGO. I submit it may need some tweaking to reflect the opinion of the spirit itself.
Current opinion: Great concept, but needs more development to reflect more variables and be adequately explained for the player.
Side note: The Divine grant Clerics their powers. Shamans aren't "gifted," they're chosen, or go through a ritual which both ask the same question: will these spirits accept me as an ambassador in the Middle Reams? If they step outside of the bounds of their authority often enough, the spirit world can rebel against them. Did you include a mechanic for that?
True Dreamwalking: Sleepy TP. Nice.
Spirit Form: The logical conclusion of it all. Also, very nice.
So those are my thoughts so far. As promised, I had coffee first.

Thoughts on my thoughts?