Been using XP Home and has been a tremendous improvement over 98 SE . WinMe was a big stinky dog (imo), seemed to have many bugs and weird things that would happen, even after reinstallations, tweaking. Perhaps just my luck (not).
One of the single most important improvements (from a data recovery standpoint) is the system restore function. If your software goes bad, or something you install makes your system shaky, you can go back in time to how it was very easily. In addition, if your computer will not boot up (due corrupt registry) and yes that can and still does happen with XP, one can follow a somewhat intricate, but somewhat easy procedure to recover most, if not all data, and place your computer back again in time to a "reliable" time. (microsoft knowledge base article 307545).
(how did I know that? hmmm) I am not a computer expert, but am becoming one it seems from time to time as events occur. I like XP very much overall, and XP Home does the job for me.
XP Home full version = $93
XP Pro full version = $143
http://www.newegg.com/software/
(with qualifying free hardware purchase)