I've ran WinME on quite a few newer machines that were supposed to be made for XP. Ran quite nice, honestly, although there was one consistent issue of the AGP slot only running at 4x, even with 4x/8x hardware...but unless you're a hardcore gamer, that's no issue. I gamed on mine like that and it ran very well....IIRC 2k Pro actually has the same issue and I currently use it on the same hardware, also for gaming.
I've found XP to be slow and stupidly easy to get nasties..even when it's updated and "secured". Put me under no thanks. I like 2k Pro and ME.
98SE is basically the same issue. You should be fine running it, but you may have to hunt down some drivers.
ME is the WORST operating system Microsoft ever created. What a buggy piece of crap! Every computer professional I know that tried ME ended up going back to 98SE and couldn't wait for XP to come along. XP Pro is great - the Home version is junk.