MechWarrior Online. And the developers are no doubt aware of this, as they've just posted a lengthy set of answers on the game's official forums, covering a broad range of topics from update speed to character development. While the answers confirm that at this point the software is still yet to see an alpha test, there's still a great deal of information therein.
Aside from a few answers that are likely to prove discordant come launch (such as plans for biweekly update patches), the team is aiming at starting off with a strong PvP environment with persistent world elements in a similar fashion to MAG. PvE will not be in at launch, but it is on the table for later release. That's only the barest summary of the information in the full set of answers, which should keep any intent pilot eagerly anticipating his or her personal 'Mech.
[Thanks to nimzy for the tip!]