Yeah, it probably isn't worth getting Combat Casting. Of course, I never got it in 3.0, when it was more powerful relative to the alternative. If you spend too much time making concentration checks you're not in the right line of work.
Unless you're a Bard. And then you should have all the meat shields charmed to avoid having to dirty your hands with the opposition in melee. Unless you want to...

Eh, Bards are weird anyway.
Seriously, though, both feats get to be pretty useless later on. DCs for Concentration checks don't keep pace with the skill bonus. I abhor taking feats just to get past the first few levels; I prefer a healthy dose of paranoia instead.
By the way, DragonShadow, who's your sig from? I notice we've got ourselves a bit of a contradiction here, sig-wise... Do attributed quotations defeat unattributed ones? Hmm...
*ponders*