Two MMO's I got some hands on time both of which are quite a ways out. End of Nations and Guild Wars 2.
End Of Nations
This game was really disappointing, I played this before I saw the developer session so I was really surprised at how not fun it was. The demo that was on the floor was a 4v4 match with capture points. It definitely feels like a World in Conflict kind of game in which you have your units and you have your support abilities. So you can call in airstrikes or deploy turrets around. The problem really is in the unit/team balance. So I had a light army and there's no real way to change this during a match. Unfortnuately for my team at the time there was seemingly no one with any anti air capabilities at all so my army ended up getting destroyed over and over again.
When I did get into a land war it was fine but with such a limited unit count maybe like 10 or so units per player it really didn't feel like you had a whole lot of strategy available to you. Perhaps this was more the fault of the demo they were showing off than the game itself but I feel like it's a game that is doing a whole lot of things that have been done better by games that are kind of already out. It will be a free to play game and they still have a ways to go with development so there are plenty of things that are still subject to change. But something like the unit count and how the units move and interact (just feels like very Red Alert 3 kind of feel, units with special abilities) I'm just not sure how this game will have the kind of strategy and depth that it really needs to be great.
Guild Wars 2
Personal bias here. So be wary about everything I'm about to say on this game. I think this game is awesome. I had a quick go on the character creation before jumping to a high level area with an Asura engineer. The character creator isn't the most in depth thing that I've ever used but there is still potential for there to be a lot of room for customization, but don't expect something on the level of Champions Online or anything.
The combat in GW2 is very different from what you would expect from an MMO, much more action focused. And there really is some novelty to being able to kite an enemy in an MMO. The game has a dodging system that's goverened by a stamina bar. The mob I was fighting was a warrior, just kind of a throw away enemy so I combined my main knock back attack and backwards dodging and I ended up killing the mob without taking a single hit. I tried some of the water based combat and this was less impressive. There's still all the dodging and stuff but it didn't have quite the same impressive flow that I had on solid ground.
Events system instead of quests also works well, you literally just walk around and you run into stuff to do. But I am somewhat wary about how many different events there will be in the final game. Only time will tell.