http://nokiaexperts.com/fennec-beta-...x-branding-n81 0-n900/
I installed this (build 5) on my N810 and was really pleased to surf with it! Especially the usage of the whole screen and fast zooming in, by double tapping! Selecting a link seems a bit more difficult because of this...
It is not slow in comparison with the normal browser (only opening, I don't care so much about that).