I have the RC and am not going any further with it.
It is XP/Vista detailed, streamlined and repackaged, that simple.
I upgraded the morning it was released and am currently running 10.6 Snow Leopard. WOW, I can't believe how much disk space it freed up! 11GB more on my HDD! I have the before/after screen shots to prove it!
Everything is faster and more responsive from launch. I have had one quirky-bug pop up... when I have Mail open and am filling in the address field, I use Address Book in conjunction... well if I double-click a contact in Address Book, it crashes the Mail app.
Odd, I know... but in the same sense, the new crash recovery is AWESOME in Leopard! It does real-time saving, so as you type/add pictures/etc. it saves that as a draft. When it crashes, you click "OK" for the report, then you're taken right back to the very character you left off on!
Other than that, to directly answer your questions Bob :
Who is going to change to Windows 7? - Not me
Who has the RC presently and are you keeping it? - I do and "No"
Anyone on Vista moving to it? No, the one Vista machine I have is stable and I'm afraid to anything to a stable XP?Vista machine!
How about you XP users? See above^
