Fantastic.
Good upgrades, variety in enemies, and the difficulty, at least of the final level was a challenge while not being too hard. Some things that kept my score from being a ten, were;
That whatever your energy level was at the end of the last level, is what you get to start the next level with. Although this may or may not be unintentional, I found it to be annoying, and when I realized I made it to the final level I wished that I had let that last jumbo walker fight it out with my mini-tesla, just repairing everything with my obscene amount of unspent cash afterwards.
That the ending was.... really weak.
That there was no joke about crossing the beams. [fake reason]