Re: Uncommitted Attacks & "Competition-style" Attacks
I don't think catching the punch is the right idea. It might work with some people, some of the time, but there will always be someone who is quicker than you are -- and if you do succeed in catching it, what do you do with it? Now you're holding onto someone else's arm, and there will always be someone stronger than you are and able to resist whatever you're trying to do at that point.
If your tactic is "I grab you and do something", I'm not sure that's aikido. It seems to me that an aikido encounter is more "You attack me, I find an opening (or create one, but that's not the same thing as grabbing someone) and do something". Maybe a better approach would be to try to figure out where the opening is in these types of attacks (for example, what your sensei says about the pullback -- if it's not a committed punch, then maybe that's your most obvious advantage and where to find the opening).