I use XP pro, and it is the finest overall operating system I have used.
I have used OSs that are better at some things, but never as consistently good in all respects.
Believe me, I am no Microsoft fanboy, but XP is the closest to 'getting it right' I've encountered.
OS Resume for the skeptical: FreeBSD, Linux (Debian, Redhat, slack), PC-DOS 1.0, MS-DOS 3.3-6.02. Novell Dos 7.0 (and DR-DOS 6.0 before that), Mac OS 1.5 - OS 7, AmigaOS, GEM (on my 520ST, more of shell really), Apple ][e and ][gs (and ][c, but who's counting?), Solaris, Berkeley Unix, VAX 10, Windows 3, 95-Me, NT 3.51-XP, SymbianOS, Palm OS, and those are the ones that I've either used daily or administered, so it doesn't count those that I've used occasionally.