I read something where if you wait a second without moving after getting on a bike you'll put a helmet on (which reduces head injury damage if you're knocked off) and apparently the same happens if you get in a car, if you stay put for a second or hold triangle or something, you'll put your seatbelt on, as opposed to GTA IV which doesn't, apparently, give you this option. Can you confirm this? If that's the case, it seems a much better compromise than NO SEATBELTS EVAR.
I did notice that your character does put on a helmet when getting on a bike.
The vehicles seem to be able to take quite a beating in V, and the controls are definitely more "arcade" friendly then the tricky cornering of IV.
I'm really starting to enjoy the story line, the characters are well acted. Being able to switch between three different primary characters is an fun twist. Actually four if you count a brief stint as a dog!
If IV was a letdown for you after Vice City, I think V has a good chance of winning you over. At least that is the case for me so far, and I'm only at 6% complete.