Wintermute is what you want to stick with if you go that route. The current version is the last one until 2.0 unless he does a bug fix release. Shaders made it into the last one and wasn't supposed to happen until 2.0 but he figured he put it in since someone would probably hack it in eventually. 2.0 will be going along those lines with more emphasis on shaders, the 3D side, and all new creation tools. It probably won't stay free, though.

You might want to look into beta testing Lassie Shepherd, too:

http://lassie.gmacwill.com/lower.php?section=news&page=index