So, I played a wizard using one of the reserve feats last night, and I'm still undecided as to whether the feat is too powerful or not.
I don't have Complete Mage with me at the moment - feel free to correct me if I've mis-remembered the mechanics.
The feat in question was Invisible Needle, which requires a (minimum) 3rd level spell with the Force descriptor available to cast. It allows the character to create a force effect as a supernatural ability. The damage is 1d4 per level of the spell held in reserve, the range is 5ft per level of the spell*, and it requires a ranged attack roll (not ranged touch). It also adds +1 caster level to force spells.
My feeling on this at the moment is that as a generic power for a character, it's not too powerful, but it seems a bit much of an ability for a single feat.
In this case, I guess the thing to compare it to is a missile weapon. My character could have been lugging around a light crossbow, with 1d8 damage and a much longer range. Instead, I was doing more damage (3d4 - I had a 3rd level spell "powering" the feat) and could move around as well.
Even if I'd spent the feat on Rapid Reload instead, the reserve feat has an impressive list of side benefits. It's (Su), which I'm pretty sure means there is no verbal or somatic component, and doesn't provoke an attack of opportunity. It doesn't run out as long as I keep an appropriate spell memorised, and the damage effectively scales as I go up in level (assuming I pick the right spell). And +1 caster level for force spells.
That's a lot for a single feat.
The more I think about it, the more I wonder if it should have some other feat as a prerequisite. Spell Focus (Evocation), maybe. And similarly for the other reserve feats - as 'second tier' feats, the benefits seem a little more reasonable.
How have others found them in play?
* This may have been 5ft + 5ft perl level.