There are some very cool physics effects you can cause in GTA IV like the one you described. One time I lobbed a grenade from my car with very poor timing, and it exploded in such a way that left a crater in the back half of my car, but the thing still drove! The rear-left wheel was practically horizontal, so you can imagine the handling was ridiculous.
Btw I know it sounds absurd, but there really is a way to get better at the driving in GTA IV. I've read enough of your impressions about other driving games (which happen to be in line with many of the posters here) to understand that you prefer an arcade racer, and GTA IV's driving is very rooted in simulation. I know that's different than the PS2 games (which were built on the engine Criterion created for Burnout, go figure), but I feel that GTA IV sets a very high bar when it comes to driving in open-world games. I'm willing to admit that GTA IV is a flawed game, but the driving is not one of those flaws. It just takes a little practice.
Anyways, you probably won't be going back to GTA IV what with Saints Row on the horizon. Game looks hot!