Gee, everyone seems to hate ME like it's some sort of devil, lol. Honestly, it's pretty stable, and I don't see why shouldn't I use it. Doesn't seem really buggy to me, and I bet half of those complaints were due to bad caps and crappy mobos (yes, I'm looking at you, PCChips.), mostly crappy hardware in general. Pair Millenium with a solid machine (a good 440BX machine will do) and it should work fine.
A few positive things and negative things would be:
+ much more refined hardware driver setup than 98SE, as well as a much more broad driver library
+ a bit more stable than 98SE - about on par with 2k, just don't pair it with crappy hardware and don't shut it down abruptly (the registry might corrupt a bit, not too much and it generally fixes it pretty fast)
+ more faster boot than 98SE - I compared a 98SE install to the current ME install that I did. 98 SE took at least a minute and a half (and mind you neither of those are old installs, both are pretty fresh installs.) while ME barely took over 40 seconds.
- no real mode DOS
- not every card gets installed out of the box - the CT5803 got recognized as a Creative/ESS card and got supported out of the box, but my other CT4810 requires me to install Creative's own drivers (CT2770 doesn't count as ISA SB16/AWE32 are basically supported since the era of dinosaurs, aka 3.1)
- maybe I've did something wrong but Catalyst Omega tends to crash when I access certain pages that are not original to the Radeon driver - I am pretty sure this is purely my own fault and not WinME screwing me up on that.