As a longtime Battletech fan but completely new inductee to the world of MUXs, I gotta say that the Frontier Lands delivers an amazing Battletech experience on my non-MWO compatible mac laptop.
I dabbled for a bit in Megamek--for those who appreciate tabletop Battletech but don't necessarily have the time for frequent tabletop games or want a more hands-on experience behind the stick of a mech, Frontier Lands has you covered.
I've been playing for the past few weeks, and I only wish I'd known about it sooner. The game delivers a seriously immersive experience--almost like you're sitting in front of a mech's nav and sensor terminal and having to really pilot the mech by engaging with its computer systems. There's a bit of a learning curve, but the depth of the game is rewarding and the community and tutorial are really good at getting you up and running quickly.
Once you've got a handle on the basic controls, the game plays like a real-time persistent sim/shooter, with a meta-game of territory control operating in the background. The game is great for short bursts of playtime and hours of play alike. You can have a rewarding experience with a quick 10-minute scrum against wandering AI pilots in an area seeing high action/capture a base by holding down the area for 20 minutes-or put together longer sortees with faction-mates for hours of fun.
The game has an active player base, but since the best thing about Mech battles is PVP, getting new players in is always a high priority.
In short, if you're looking for an online tabletop sim experience and MW:O isn't doing it for you, grab a MUX client and give this game a whirl. Alternatively, if you like Megamek but want to do some real-time Mech combat, this is the solution. FrontierMux incredibly rewarding, astonishingly immersive and just a ton of fun.