Hmm. Interesting.
Part of the problem may be that I'm a "classic" defense game fan. I like the idea a lot, but right at the beginning I have a problem. It's difficult to place things -- there's no indication of where they're going to go. That's a big stumbling block for me, and it seems like a major UI error.
Also, due to the single 3d viewpoint, it can be hard to see "behind" things. Maybe a slight opacity reduction to help with that.
I want to keep playing, but object placement is definitely a problem.