I'm surprised by the lack of heists thus far. I'm about halfway through the game and there's only been two, and the second one (the mini-sub one) didn't even feel like a proper heist because I didn't have to hire anyone for it, just pick between two methods of pulling it off. I just got a call to go visit that guy whose house Michael destroyed early in the game, so I assume he's going to drag me into more heist action, but I wasn't expecting the game to take so long to get into the main heist stuff.
Driving while shooting is a pain, it was much easier in GTA4 even though the mechanics of it are almost exactly the same. I think that the changes to the driving mechanics make car chases much more rapid, making aiming more difficult than it used to be.