I think the problem most people are gonna encounter is that if they don't work as a team (particularly in squads), the game is much harder than BF2. I was frustrated when I started and kinda hated the game since I kept trying to do things on my own and was constantly getting killed. Getting points is no longer a breeze like we are used to. Particularly with kills being worth only 1 pt if you just randomly go and kill people. You've got to follow orders this time, work as a group, and help people out to get the best scores. When you do that, you'll feel in sync with the game and it really is an amazing experience like majorassault was saying.
There's still some polishing to do in the game, I mean it is still a Beta release, but I can't say that EA and DICE didn't put a good amount of time and effort (and money) to make a better game than what BF2 is. At it's core, BF2 was still experimenting with the persistent stats and unlocks idea which was a good first attempt, but 2142 definatelly brings it all together in the end. (BTW, I favor team-work in games a lot, I know most people don't, so opinions on this are bound to vary).
In the end, it's similar enough that it might come down to personal preference like some of you have said. Those who don't like the futuristic setting will probably stick with BF2 and POE, and they won't necessarily be missing out on a huge amount (like BF 1942/Vietnam to BF2 leap with the stats and unlocks). But at the same time, there's oh so much more to enjoy in 2142 that, at least for me, gives the game more replayability value than it has ever had.
Oh yea, and the vehicles take skill this time around, that's why some people hate them... and you can't go at it alone anymore either (recurring theme you notice). You will benefit a lot by having a secondary gunner in all the vehicles. For example, in the tank, main driver only gets to shoot tank shells. Secondary gunner has anti-infantry gun. Unless you're working both, you make an easy target.
Tank whores won't be the same anymore I am pleased to say. I'd like to coin the new term for the future though: Tank Whore Duos