Overall I must say that I'm dissatisfied with the performance of Win Me because of the questionable claims by Microsoft to have improved this OS. In 3D testing, the OS is nearly on par with Win98SE even though Microsoft claims to have improved overall performance of this OS. In hard disk intensive testing like Sysmark 2000, things only got worse as scores were clearly lower in Win Me. Switching to Win Me will, without a doubt, cost you some performance in everyday use.
Aside from the various benchmark scores generated I did spend a fair amount of time with Win Me on several machines, including one at home. For the most part the OS was stable on my everyday applications. System Restore is annoying and it does noticeably slow overall system performance down when enabled. Toggle it off and things might actually be ok but unfortunately it turns itself on after a crash and randomly at times so you'll have to live with it until a fix is created.
Win Me might be a useful OS for new PCs as it's basically a slightly slower version of Win98SE with all the latest Microsoft programs and updates. The performance losses should be transparent to your average users but not likely for the tech groups. Users of Win98SE should have no real reason to upgrade to this OS in my opinion, at least not yet. If your current machine is running stable in Win98SE, I wouldn't bother taking a chance for the time being until a service pack for Win Me makes its way onto the net.
Microsoft has yet again released an OS that raises many questions. Why do we really need this upgrade? Why is it slower? How come Microsoft is trying to incorporate more free software packages into their "OS" that have nothing to do with an OS? Netscape and the browser war come to mind. If Microsoft would indeed improve the actual OS itself instead of adding so many useless features, we might have a real reason to run out and buy Win Me.