First of all, remember that this review is of the game in it's prealpha state, and as such, it obviously has a more restrained outlook on things like bugs and glitches. The game has just been released to early access, and that's so that the devs can get feedback on what feels right and what they can change. Don't expect it to be a fully fleshed out game. It's still in development. There are multiple bugs and little things that could be changed with the engine (the audio is quite odd in the boss fight, there seems to be really bad collision code...), but overall, the engine is fairly well fleshed out. In my thirteen minutes of play (unfortunately enough to see pretty much the whole game), I didn't crash or have any major lag issues.
Now for the actual game design part. See, the game is all about driving your mech warriors in voxel landscapes and shooting stuff in various game modes. There will be a crafting mode in the future, where you can build levels using a voxel engine, however when i opened it I couldn't find how to build anything, so I'm assuming that the crafting mode isn't fully fleshed out yet. The voxel engine does two things mainly. It makes it so that you can destroy the terrain (always great fun, as there are nice particle effects when destroying things and also for the sheer sake of destroying), and the voxel engine also allows the player to craft. ATM, it's mainly destroying.
The main game mode is somewhat obtuse in what to do atm. You have to destroy certain objectives, in order to convert them to your side. I didn't know what these looked like until I realized that they were these small rods that you had to shoot. Once you have converted a few, the boss comes in from the sky. He's massive and certainly quite impressive, but the way he walks on the ground makes it obvious that this is an early alpha game. He somewhat floats to the highest block, and it doesn't really look realistic. Overall, the game mode is just a way for the developers to test out the engine and to demonstrate what the game might feel like when it is done.
Atm, the game doesn't feel like much. It's basically a version of Hawken where the mech handling doesn't feel as nice (If you shoot out a 1 block wide wall you can walk in there. It feels like you're a small person with a mech shooting hand). However, I can see the potential in this game. I especially liked the feeling of verticality in the main level, as I could blow my way through the various obstacles while dodging shots and firing at the boss down below. However, staying on the ground was quite glitchy as I would bounce around the various cubes (Not exactly Minecraft movement so far).
So overall, would I recommend you buy this game? No, absolutely not in the state that it's in, unless you want to help design it. It's not at the level of the Minecraft alpha, where you already have a game. It's basically a tech engine with good potential. However, if you want to help design the game and give feedback on it, I suggest you get it.