I respect SKR, but I almost literally LOL'd in front of complete strangers when I read the text of Combat Casting:

"since most of the time you're make Concentration checks are in combat so it's in your best interest to take this +4 feat over the general +3 feat"

You only get the bonus when casting on the defensive or when in a grapple.

If you are casting on the defensive or when grappling, you probably have not done something right, and that extra +1 ain't gunna help you. But that extra +3 may help against that archer or monk that is trying to disrupt your spellcasting through damage (which is not covered in Combat Casting)...