With all of the collectibles, I really wish they had some in-game way of finding them without having to have my tablet open with maps and screenshots to tell me where parts/scraps/paintings/etc are. Even something as simple as a "somewhere in this area" circle like they do on some of the missions.
The garage/impound thing still pisses me off. I can maybe see it on cars that are stolen, but on stuff that I buy legitimately? Those should be perma-stored in the garages just like your character's standard car.. if you leave it somewhere or it's destroyed (which is inevitable), then it just reappears in the garage a short time later. The game can already do this, because it works with aircraft. I crash my choppers all the time, and they're always back at the helipad the next time I go there (Franklin's stolen choppers, not Trevor's story chopper).
Minor gripes in the grand scheme of things.. I've already put a shitton of hours into the game and I'm not even done with the story yet, much less all the side activities.