I am also a COD (or was), I have seen Battlefield 3, and I've played a bit of Gears of War; never once, though, have I played a Ghost Recon game (other than GR:FS).
I expected a really great game, but I didn't have any of the other GR games to compare it to, so I was pretty open to a different kind of shooter game. And I absoloutely love the beta for FS! The cover system is amazing, I love the gunsmith, and, having played COD: MW3 not twenty minutes ago (I was waiting for the FS server to go back up), I was just itching to get back to FS. I missed the shooting range, the cover system, and the third person perspective; so much that I only played two matches of MW3!
I am blown away by the beta for this game, and I cannot wait for the full game to come out!
(P.S. The only thing(s) I don't like about the beta is that it is very temperamental with the server working or not, and you can't do ANYTHING on there without the server. A sampler of the other game modes would be fantastic!)