
Kalrik |

Combat casting is a must if you intend on being in combat. Clerics, paladins, inquisitors, magi, etc will be in combat and casting spells, which is exactly where you need the feat.
I never pick it up on my wizards, as Abraham spalding, said, I keep away from things that hit me. Once you get access to invisibility/fly you can place yourself where you won't need it.
Finally, Combat Casting is only good for casting defensively, there is a trait, focused mind if memory serves, that gives you a +2 to all concentration checks. This is much better than combat casting over-all, but still unnecessary.

Khrysaor |
Never take this on a magus. It's a trap. Unless its an archetype that doesn't get any bonuses to casting defensively. It also gets easier on all magic classes that aren't full spell progression. Max of 27 before modifiers like disruptive is near impossible to fail on any class. Also a 5' step is usually enough to avoid it vs medium or smaller creatures.