I tried this out - it's pretty neat - good job!
Two minor comments:
- any plane created goes away when exiting the wizard. Is this intended? - I found a typo in the code (spacing) on line 112 & corrected it
Hmm. For my purposes when I made it, cleaning up on exit was the right thing to do, but I guess other people might want it not to. Wizards are a little too simple for preferences...
If I ever manage to make plugins on OSX, then a plane (or geometry!) plugin would be more flexible.