Played the beta for roughly 4 hours and found it to be pretty damn amazing. Definitely glad I preordered this, brings back good memories from 2142. Seems pretty refined too. I especially like the new knife and the fact you don't get tired after sprinting for 5 seconds anymore (infinite sprint). Knife feels a lot more like a weapon that it does in cod4, and even the older BF games, though you now use it on a melee button instead of a seperate weapon. Takes some skill to get it right, but I find that to be a better quality than everyone just randomly slashing in a direction like in cod4.
The enemy spotted now works by pressing Q while looking at someone and works great. You can't see anyone on the map until someone spots them, and if a spotted enemy dies, the spotter gets an XP bonus. There are A LOT of unlock, pins and rewards. If you're any good at the battlefield style play, you'll level decently fast and get a lot of them. And nothing's actually more satisfying than checking out all the rewards you got after the round ends (and you can take your time doing it too before rejoining the game, damn you cod4). Of course the dog tags made a return. You get unlocks for a class by playing it, and it takes you linearly through the tree. But honestly, I prefer this over the old system. It seems you get stuff a bit faster, and it's working good so far. Also, some unlocks are universal for all the classes, like some rifles, and handguns. So if you've been playing a ton of engineer (like I usually do), you're not gimped when switching on to assault later.
Anyway. Love this game.