Ubisoft's games are pretty sloppy on PC. I have AC4 for PC and it doesn't run too well because it pretty much requires you to have V-sync on unless you want your game to look broken. As for the 30FPS, that is actually not true. Their games are not officially locked at 30FPS, but when V-sync is on and your game does get pretty hardware intensive (big cities, major fights) the frames will start lowering from 60, and you have a 60Hz monitor, it will automatically go to 30FPS and hardly goes back to 60. It gives the illusion that it is locked down at 30FPS (which in a technical sense it is) but will still run at 60.
I just hope Ubisoft will stop screwing over PC gamers (they said they would, but I have yet to see it). As of now, your best bet is to get all your Ubisoft games for PS4 or XBONE unless your like me and don't want to fork over $400-$500 for a new console when you have a nice working PC and PS3.