QFT.DMing 4E is a relief.
Conclusion: In my experience, 4e has done more to encourage players to try their hand at running games than any other RPG I can remember.
QFT.
A rundown of my gaming groups:
1994 to 2008 (3e/Shadowrun/Champions/Gurps/WoD/DitV/Buffy/etc.): 3 GMs out of an average of 12 people.
2008 to present (4e D&D only): 5 DMs out of an average of 10 people.
Conclusion: In my experience, 4e has done more to encourage players to try their hand at running games than any other RPG I can remember.