The full version costs $9.99 Canadian dollars on steam, but the free beta version is-well, free at http://www.buildandshoot.com/
I for one think the new version is better, but doesn't fit in with the original's idea of being a slightly slower paced game where you build everything then shoot and repair cover.
Ace of spades steam version shouldn't be called Ace of Spades. The beta, is also nice, but as I said, it's really slow paced and there were too many hackers.