If my defender is at all tangled up with a guy, he won't jump when I hit the button; I can't seem to go up for a block unless I'm so far off I'm not playing tight D; I wish it would just give you a weak attempt at a block or an awkward attempt making a foul more likely, instead of just not doing anything.
It seems like guys never try for the steal either...
That said, I think the game feels a lot better than '05, I never played '06. I seriously doubt that they'll leave the substitution bug unfixed; since that's more a matter of something integral being completely broken than a minor gripe or glitch, I really do think it will be patched.