Simple as this, a lot of people say the online is amazing and thats where its at, yeah i will admit, it is awesome online but there are a couple of problems with it. Let's start with the fact that you start with 3 classes each with an unlockable 3 guns....thats 9 guns, then you unlock the veteran versions, which are completely useless. Also there are only something like 5 or 6 maps, then 3 on the Combat Mission game mode, they say they will release DLC but lets be honest, you should have them with the game.
Now Single Player.....terrible, slow, buggy and very disappointing from Dice, I expected something like Bad Company 2, unfortunately this isn't it, and the Battlefield 3 Beta isn't BF3, it is the extension to Battlefield 2: Bad Company 2 entitled Vietnam and quite simply should just wait for Vietnam or stick to your guns with Bad Company 2 or buy Black Ops.
All in all you want some easy Gamerscore, wait on the price drop and purchase this, but like I said for near 40 pound this is terrible. The gameplay isnt smooth, but the graphics are OK,nothing special.