I've only ever DMed 4E. I used to be one of those guys who'd never ever DM, I thought it was a sacrifice some selfless all-knowing sage sent from the heavens had to make so the other players could have fun. 4E was the game that lifted the mystery veil of DMing for me, making me realize DMing in 4E is EASY and FUN. I sucked at first, sure, but I'll even go as far as considering myself a "good" DM these days.
I'm getting a new campaign ready right now. I'm doing as the "pushing the envelope" thread suggested, had this idea in my mind for a while: running a 4E old-school style campaign. Healing Surges are a perfect resource to deplete. This way, even a dumbed down encounter with 1 or 2 monsters can be taxing, and non-linear exploring becomes an interesting risk/reward endeavour. Throw in some dungeon dynamics, old-school monsters and have tools handy to generate encounters on the fly with zero railroading, and there you go.
With no shortage of options for PCs and DMs, and also seeing how easy it is to reskin and create your own monsters, I know I could play 4E until the day I die.