It shouldn't be hard to get into the beta and see for yourself since it seems like it'll be around for a while (say it's done on 2/28/10 in its information profile). DICE has been posting codes on Twitter and probably Facebook, too, so there are a ton of codes out there.
I've played a couple of hours and it's a lot of fun. I haven't played Modern Warfare 2 to compare, but I'm having more fun than I had in my limited time with the first Modern Warfare and Bad Company. I like the huge amount of unlockables for each class, vehicles, and other ways to play the game. I like the way rush mode is more balanced here than what I played of BC's beta, as I've been able to win on defense and offense most of the time and it's a well-balanced game. Tanks can be a bit overwhelming for the first alpha/beta area, but their usefulness shrinks the further I've gotten into a match. It's even been a good beta for working with others cooperatively whether I know them or can talk to them, which could change by the time the general public gets their hands on it. It could be coming out at a good time as people may get all they can out of MW2 by March and want something new, though IW could counteract that by releasing new map packs a week or two before BC2 is out.