On Windows Vista, for me atleast Firefox 3 latest 21 march nightly trunk sux right now.
Feature wise my IE 8 beta installation is as tweaked as my firefox with extensions. They both support 99% same features now so the choice is between rendering speed & look & feel only.
Rendering speed wise firefox is better then IE 8 right now, but I can live with .2 nano second delay in IE 8's rendering of a page, however the look & feel of firefox on Windows just sux right now.
In IE 8 I can enable cleartype for HTML. Now I have a CRT monitor so system wide cleartype looks bad on my monitor. Despite of this I can enable in IE 8 cleartype for the HTML rendering only which makes reading things very easy. On the other hand in Firefox there is no such option, & I either have to live with non Cleartyped text in firefox or with system wide cleartype which looks bad on my CRT monitor.
I mean, comon.....IE 7 had cleartype for HTML since ages, safari too has it... I don't know about Opera, but why isn't this in Firefox 3 when they have a new rendering engine & Cairo Support.
The memory usage has improved, thanx god....
The new Vista-ish theme sux. Period. I expected something better like the mock ups from Mozilla.