I've DM'ed everything I could get my hands on in the last 25 years, I'm not a player- I'm a control freak; so 1E, 2E, 3.xE, Paranoia, Runequest, MERP, WFRP, Rolemaster (oh God), and lots of others I can't remember right now.
I DM 4E now via Maptools & Skype with people from all over the globe, I figure I'm 50 encounters ahead of the game, all maps done- just everything prepped and ready to roll, I have never had it so good- I do loads more window dressing these days, ready to roleplay, such is the time I have to spare.
At present I am so far ahead I am scratching my arse as to what to do next to keep me amused between games, I can build a session's worth of adventures, including all maps et al in an hour or so.
For the records I hated 4E on first look, those days are gone- 4E sold, where have you been all my life, and simplified- well, yeah. Just add some depth elsewhere, works for me- houserule the complexity back in if you have to.
Saturday I'm going to build 30+ level 1 PCs using D&D Character Builder, then Macro them all up in Maptools- I reckon it'll take me three hours if I listen to the radio and watch TV at the same time.
Easy life, 4E every time.