i use this below Firefox build in Vista right now...
Tete's Firefox 2.0.0.3 [2007032116 en-US win32 tete009 sse pgo]
Visual C++ 2005 SP1 (PGO) build, and CPU Instruction Set SSE3 Beta DLL (December 8, 2006) -
http://www1.plala.or.jp/tete009/en-U...html#FFRELEASE
when tested with no Add-ons, no Flash (Proxomitron), and with 50 tabs opened, i can hardly see any system performance drop off/down.