The game works for me. Steam should give you a 16-digit alpha-numeric code when you purchase. Put that in the Securom (grey pop up) box in the blank line. Don't worry about the other long code (25 or 30 chars), it's generated by them to verify the game. After successfully going through this process once, you should be good. It won't happen every time you launch.
The Gamespy servers are off, so there's no multiplayer, leaderboards, or map generator, which does suck, but you'll be able to get a dollar's worth from the 21 pre-built scenarios.
If Steam could somehow separate the Gamespy servers from the game, even just to open the map generator, that would add a lot. Single players could generate their own maps and choose the number of AI players and win conditions. Is that remotely possible from a programming standpoint?