I've never DMed, but I really want to. I'm gonna start working on a world and campaign from scratch (it's ambitious, but I really wanna use only my own settings/adventures) this year, and hopefully get to run it by early 2011 at the latest.
I wouldn't have switched to 4e anyway because I don't want to shell out for the books. (I have some PDFs of the core rulebooks, but for D&D I really find it important to have the books.) I read through most of the new PHB, and I was really disappointed by the overhauls. I agree that some things, like attacks of opportunity and encounter levels, were a bit complicated (but not to an unusable degree! just confusing), but some of it is just too far. I mean, getting rid of skill points? That's too much. And from what I remember, the spell system is severely different now, with many fewer spells and a generic sort of description that allows rogue abilities to be pretty much the same as wizard spells. I really love the hundred or so pages that the 3.5 PHB dedicates to spells alone, and I was very unhappy to see that truncated.