In an earlier post I can't find now someone mentioned Kirk seeming to not have a problem hanging out with them in The Final Frontier, and then hating them with passion in The Undiscovered Country. I think this is the thing that bugged me the most, the sudden change in attitude between the movies. I understand a bit of time passed, but it still seemed like a drastic change. I understand people's feeling can change over time, but if these feelings are supposed to be brought on by David's death, then I would think they would be stronger closer to the event (TFF) than farther away (TUC).
The only (lame) justification I could come up for that is that Kirk had been too busy with the Probe incident and the Enterprise
-A's maiden voyage to really process what had happened. A delayed reaction, if you will.
Honestly, though, I think I've watched STV about three times (as opposed to at least a dozen times each for STII, STIII, STIV and STVI), and I tend to just ignore it. I think I once heard the theory that all of STV was just a dream that Kirk had on the camping trip with Spock and McCoy (or maybe some sort of weird shared dream between the three of them). It just allows sooooo many things to be explained away, and since STV is referenced so infrequently, it's not that bad.
I mean, obviously that's just me applying my personal continuity to the discussion, but, yeah.
One thing that has always surprised me is how much time passed between STV and STVI. One of the biggest gaps between movies we have.