Well have managed to get SP2 on Mini 9, after running vsp1cl.exe to create sufficient space to allow SP2 to install and after running compcl.exe after SP2 - and using unmodified install disks (ie no vlite) have ended up with 3.62 gig spare on a 16gig
SSD - as compared to a much lighter normal XP install. However all things including aero work, have set specified pagefile limits, disabled system restore and to be honest it actually runs not bad - had OSX10.5.4 on this prior to installing Vista Ultimate and really not much to say between them for speed - Vista actually seems OK, weird yes I know but looking froward to running the final version of windows 7 just for comparisons sake.
Have also run multiple cleaners like CCcleaner and wise disk cleaner, have also left all the eye candy turned on just to see how it performs.