GTA Online sync seems to be way worse than even samp's, look at the bike's unnatural movements and jumping back and forth (unless the guy has terrible internet)
I think it's only really a problem with people with bad connections, I have found synchronisation on the whole to be very good in GTA:O.
However, the gamemodes are very boring and there is a huuuuuge wait between doing just about anything (too many silly transitions and lobbies imo).
I don't know why they can't just copy ideas from the SA:MP community, ah well, only a few months to go...