I played one laggy 4 player game last night, but it was still fun even with the lag. After that, i joined up with a gaffer from the gaf gamertag, CQQB or something close to that, and we played 4 player for a while without any lag. Jumped on today with my brother for 2 person multi and it was lag free as well.
Overall, I really like the game. The customization is fun, and I'm always a sucker for these Tower Defense games. For 1200 space bucks, it's definitely worth it.
I feel like the engineer chassis' are hard to use by yourself. More emplacement choices don't really matter when you're still so limited on funds. At least in multi, you can get your teammates to level up your emplacements.