I've been using XP Pro on my desktop since it came out, without problem (by that I mean, less problems than all previous Windows -- obviously Windows always has problems).
I've been using XP Pro on my car computer for about 3 months. I experience less crashes. About the same bootup time. Journaled filesystem (no need for scandisk, no worries on corruption). It does the trick. I wouldn't go back to ME, though there was nothing really wrong with ME.