I haven't extensively tested this mod, but from what I've seen it's pretty good. The MEC animations are pretty smooth, aside from its feet clipping through the floor of the Skyranger during the Mission Briefing/Closing sequences. The Viper has a few more issues in terms of its animations. It seems like it doesn't work well with cutscenes outside of combat, going rigid and phasing its layers through each other on both the Mission Briefing/Closing and the Skyranger Landing Deployment sequences. In actual combat, the animations flow smoothly, though the tongue grab does have some slingshot issue where it moves them to strange places. I had a Viper teleport into the ground at one point, though they could still be targeted. I just got a Muton, so I can't speak about how well it plays. I should note that I've been playing where the aliens cost resources and/or time. So far, I feel like they've been fairly balanced, especially since you get them as highest soldier rank-1. MECs are remarkably easy to get, but considering their low aim and low damage output, I don't feel that's too bad. However, getting a bunch of MEC's could be really broken, since they heal at 400%, and with the AWC, I was able to get a MEC that was knocked down to about 1 health back in 3 days. I feel like the "Artillery" branch of the MEC could use a bit of a retool, perhaps getting something similar to the Infantry's Light 'Em Up in order to fire a bunch, or maybe more explosives, or improved explosives. Right now, the base aim of the MEC doesn't feel like enough to validate a lot of the Artillery route. A +10 aim if you don't move doesn't compare about moving to flank, especially on a character that can't take cover. Aside from that, the mod is pretty fun. I find myself using a mix of alien and human units, so I don't feel like one clearly outranks the other. The earliness by which you can get MEC's is a little strange, considering I was able to grab one before I had even fought one, but I genuinely enjoyed the "rescue" mission. I look forward to what else this mod will bring!