heres a tip for some people that i worked out (quite stupid that this works really): if your car breaks down (car will not start, i dont mean that it has blown up), just keep holding down the right trigger, bring up your phone, type in any number as it doesnt matter what number, call that number and when you either get the enganged tone or someone answers, your car mysterially springs to life!
also seem a few more bugs and things that annoy me...
if you park your car between two thing (a wall and a tree for example) and it blocks both of the front doors, try to get out and see what happens. the car suddenly flips on its side and niko then climbs out the door.
the clinging to walls feature (a la GoW style) is buggy and quite crap. first of all, he moves slow as hell while hiding behind something, and can sometimes be hard to control. sometimes, if your in the right spot, and you try to cling to a wall, he will actually cling to a different wall anywhere within 10 metres around you, for example. i was standing at the top of a flight of stairs and wanted to cling to the railing at the very top of the stairs, so i pressed RB, and niko ran (faster than he can actually run in the game) to the bottom of the stairs and clinged to the railing there. ive totally given up on this new feature and just end up crouching behind something.