On my system ( 3.4 GHz Dual Core P4, 80 MB Sata2, 2 Gigs RAM, 10 meg internet pipe ) web access is actually faster with the cache disabled.
With it enabled, I can watch the screens draw on the screen.
With it disabled, the screens just pop in.
With v6 ( same system, different drive (80 gig IDE) ) the cache was always on and the system did not appear slow at all. I never tried it with the cache off.
Is this something to do with v7 not liking SATA drives, or some other querky thing?