A personal opinion automatically disqualifies me? lol okay if you say so...
Keywords:
depends - what you are using it for, what version, etc
out of those I would say - expressing my own personal opinion and experience with everyday use
Don't get me wrong, Windows 2000 is great in some ways with networks and being rather stable, you can tweak it into something hardcore, but it's not really worth the time due to graphic issues.
I even know a ex-Microsoft Staff member that called Vista a piece of $h!t which should of never been released and Win7 will become it's replacement. I've used it a while then moved onto a beta version of Win7 when it came out, the beta was 20x better, the final version I now use and wouldn't dare touch Vista again - there's just no point for it! Even Win7 has been corrupted with Vista look and feel, so if you like Vista so much then your'll love Win7.
I've tried them all as I own a MSDN subscription. I still like WinXP overall and Win7 is quite nice option if you perfer Vista styles.
I've also benchmarked them all except Windows 2000 on the same hardware - WinXP best performance. Vista is a memory hog, not that people care! Win7, not has fast as WinXP but better quality graphics due to DirectX10+.
ps. Thx Allan for the complement, thats the nicest thing your ever said which is more than one word long! I don't know maybe I should change my Experience from 'experience' to 'expert' now, it's not that up yourself right? I mean it's still under you Mr 'Guru'!