I purchased notebooks with each of the o/s's mentioned above (98SE, ME, 2k, XP Pro and XP Home) preinstalled (and desktops with 98 and 98SE), all labelled with the "Designed for Win [version here]" label attached, at least a year after the OS was released. I would rank ME far below the others in terms of stability. Whether these were driver compatibiltiy issues or not is irrelevant. As an end-user (and not a system administrator/techie) ME was a nightmare. All I did was install Office 2k on my ME system (which came with ME preinstalled and all the drivers were ME certified from the OEM - Compaq) and use it for light word processing and e-mail/net surfing, and it blue screened a lot more often than 98. So much so that I was leary of newer windows versions and stuck with the 98SE machine before discovering that 2k was a quantum leap over both in terms of stability. I switched to Win2k late in 2001 and finally bought my first XP Pro machine in March 2004. I'd rank 2k slightly ahead of XP Pro/Home for stability and speed, with XP far ahead of 98/98SE and ME dead last with a comfortable gap separating it from 98. I still use the original 98 machine, which has been upgraded to W2k, and it is ROCK solid (remarkable for a notebook that is 6 1/2 years old). The ME machine, too, shines with Win2k installed and is still in service with my sister, who uses it in exactly the capacity I had envisioned for myself when I bought it (light office duty and e-mail/Internet). I've numerous friends that had the same experience with ME preinstalled on notebooks/desktops from major manufacturers. The two XP machines see the most use now and are very solid, though I remain convinced (and it's a gut feeling only) that the Win2k machines (which saw two years service with me before I moved on to XP) were less susceptible to blue screening.
Just my 2 bits - an end-user's perspective.