I have played Farcry 3 for a bit (~10 hrs). Wasn't a bad game by any means but i would agree with Vilham about repetitiveness. I'm usually a big fan of open world games but there was something missing there to keep my interest up.
Maybe it was the structure with the towers. So i got 3-4 of them and then i know alraedy i will do the same thing over and over before i finish the game. It didn't feel as rewarding/enjoyable as exploring does in a Bethesda or Rockstar game.
If you can improve on that in FC4 then it will be on my radar for sure.