I've also been playing in the beta, for about a month now. The game is fun and has taken me away from TF2 for a while but I dont think it has the staying power. I've played as Soldier and Commando, lvl 10 soldier, lvl 3 commando now.
After playing in such a relatively well balanced game like TF2, there are some significant weapon balance issues. (i.e. knife versus SMG, tank vs dynomite). Team-based play mechanics isn't very strong--it is too easy to play as a lone ranger. There are some interface glitches and functional issues (okay, it is a beta) that are pretty frustrating, i.e. after you die it cycles through each other player's view with a lot of loading/kludge wait times.
Weapon variety isn't satisfactory either. You basically get 1 of 3 SMGs, 1 of 3 handguns and 1 of 3 shottys. Each is basically the same model with differences in ammo and effective range, but not enough to really matter.
Vehicles are fun to drive, including the planes. placement of AA guns on the maps doesnt make much sense. Running people down in a jeep is pretty fun.
The Battlefunds are confusing too; I fully expect that if I put down cold hard cash that I can purchase advanced weapons. Not super OP but at least distinct. That's not the case. But you should see my "I'm with Stupid" t-shirt and grenade belt. I'm not kidding.
Anyway, I agree with rotide's review in many respects, but this is definitely not like TF2. Much more casual game.