If you've ever used Blender and are also interested in making games, allow me to link you to the Blender Summer of Documentation Introduction to the Game Engine.
It sounds as if there is plenty of functionality, but looks as if the learning curve might be hefty. The author says no experience with Blender required. I might report back if I take a crack at it.
Perhaps this would be a good tool for early prototyping, especially for small teams, or for companies that don't want to throw a lot of resources at something without a proof of concept. I could definitely see an artist/programmer duo collaborating - if they only made some kind of networking capability (the way Writely allows simultaneous editing).
It's nice to see the confluence of these tools. Blender has a nice UI with a lot of the wrinkles smoothed out of it - one of the benefits of open-source.