A tip: it seems that the registry hacks to make Internet Explorer 7 go faster on Windows XP (including making new tabs open faster) also work on IE 8 beta 2. They did when I tried them anyway, being a speed, optimisation and productivity freak!
So if you want to speed up IE8, you could try the IE 7 registry hacks on IE8 - I've produced some .reg files which you can use as a shortcut instead of having to open the Registry Editor yourself, see the previous post which has full instructions on how to use them.
If you had previously done the registry tweaks on IE7, then installed IE 8, I suspect the old tweaks got overwritten in the process. Re-doing the tweaks has certainly made noticeably speeded up my Internet Explorer 8 beta, anyway.
(The other IE7 tweaks I previously blogged seem to already have been made as standard in IE 8 beta 2, or haven't been wiped out by the installation of IE 8 but you might want to double check especially if you hadn't tried them before on IE 7.)