Imo the game lacks the perfection of COD4 concerning gameplay, graphics and sound.
Yet I see a certain potential for this game, if they fix the lag problems. I played both SP and MP yesterday... well SP is ok, nothing spectacular so far but I guess worth playing nevertheless.
MP, yeah well... lags, absolutely useless team members ( yeah we totally need another sniper on the rooftop when our last gold target gets destroyed and no, please don't use one of our 2 empty tanks why our base gets raped, just run into enemy fire and die again ) and some, well let's call them imperfections concerning collision prevented massive fun. Also getting used to the helicopter might take some time, very questionable control scheme there if you ask me.
Conclusion :
I'll play the demo a little more, maybe with friends who have an idea of tactics and then I'll probably buy it - it's a nice addition to COD4, although I really don't see BF BC getting close to its class and perfection ...