Yeah it did seem stupidly easy to smash up vehicles in GTA4. I know having it explode in a populated area can be hilarious but it's really lame to feel like the slightest scuff will turn your rare gorgeous vehicle into a pile of shit that explodes. It'd be nice if there was a bit more stickiness to cars too, i.e. they don't just disappear forever when you go a block away or do a mission. It was hard to really feel like it was worth investing in/keeping cars in IMO because I know it'd just end up disappearing because of some mission or some random crash.
Is the amount of buildings you can go in about the same as GTA4 too? I guess there are still lots of mission buildings to go in, but it would be nice if more shops and shit were usable.