I have a few complaints about the reliability and the game design. First, the game does tend to crash to desktop with distressing frequency--usually when switching from one screen to another, which can cause a loss of a complex deployment as you go to edit a ship design. It's never crashed mid-battle, though. Second, given the multitude of ship designs you're likely to make, the tools for editing and filtering them could be better.

Gratuitous Space Battles is inexpensive and is actively supported by developer Positech Games (an expansion pack was released in December of 2009 and more are promised) and a vibrant community. The demo contains just enough to get you hooked--you cannot unlock new weapons or ships, and there's only a few scenarios to play with--but that was enough for me. If you like the gameplay enough to burn through all the explosive and tactical possibilities in the demo, you will be very happy with the complete game.