Vista takes up about 4-4.5 gigs worth of HDrive (more than all previous windows OS combined I believe)
The new Windows 7 (which appears to have the same interface as Vista) will take only 0.5 gigs of HDrive and be much much much less resource gluttonous.
The reason for the early release is because only 3% of companies actually upgraded their OS to vista to date, while microsoft was projecting 25% of companies to have upgraded already. I believe everyone is waiting for someone to say the OS is finally "stable" (but lets not forget XP didnt get stable till SP2)
I've used Windows 95, 98, NT, 2000, ME, XP, and now Vista
Oh how I miss '98.
Vista reminds me of windows ME, the operating systems no one wants :-(