I don't think I could ever do 2E again. 1E, maybe, but I never used 2E, anyway. It was more like 1E with some rules cribbed from 2E (rangers can sneak, thieves distribute points, etc.). But that's a hair split, in comparisson. I don't think I'd go back to 1E, either -- the core d20/3E engine is much better, IMO.
One thing I have considered for my next campaign, though, is to use only core rules. Expansions (Complete X, etc.) will be either verboten or picking single rules from them for specific needs, but not generally advertised. There's a good chance some of the tweaks from UA would make it in, too.
Speaking of UA, if I really wanted a simplified game, I'd use 3E, with a couple of modifications from UA. First, use the level-based skills option where there are no choices involved -- in class skills are equal to level, cross class skills are 0. Second, use the generic classes from UA with no PrCs. Warrior, Expert, and Spellcaster are pretty straightforward and generally easier to manage than 13? base classes. If you do those two things, you've pretty much got OD&D running with a more stable base. Sure, you've got feats, but if that's the only complexity, you're fine.
If you want to refine things further, you can always pull in some other variants, like the UA facing rules.