@Venturesome: While detailed information about rare units isn't available, you can always stop by the Formation Editor and deploy your Infinite Fortress there. You can at least get an idea of what it looks like and its basic function.
Or, just go ahead and take it for a spin on an easy level! Either way, if you decide to keep it you can drop it in your Unit Bank on the lefthand side of the screen.
Insanely fun. The twist of being able to build units for free was a big help to making the game NOT feel like a chore, as some defense games do.
You know what I thought would have helped most? An option to make all your units' health bars visible at once. It might slow things down some, but it would sure help me figure out what parts of my base need support and healing.
Thanks!