Holmes Basic, moving swiftly onto AD&D, as the books were just starting to be available. DMed my first ever game and kept on doing so - I never actually played D&D in those days, just DMed, though I did play other systems.
I then spent over 20 years GMing and playing other games - mostly RuneQuest, GURPS and Vampire. Got back into D&D a couple of years ago, not without a little scepticism, but I loved what 3.5 had done to the game. I still find it a little rules intensive at times, and get frustrated when everything grinds to a halt because the DM doesn't have an eidetic memory and we have to look something up. I also struggle to make the rules give me the character I imagine when I first cook up a concept.
But overall I like 3.5 a lot, and besides that age has made me worry a lot less about rules, as long as the game is fun.
As for 4E, it looks like it will answer a lot of my niggles with 3.5, but only time will tell. Our whole group is only just back into D&D, and a lot of books have been bought in the last 2 years. I could afford to buy new ones, but not everyone could, or would want to.
I like the direction Wizards say they're taking 4E - the philosophy behind the changes, if you will. I won't know if I'll like the reality of 4E until it's out, but I'm sure I'll buy it to find out.