Firebird slow? From my Athlon XP running WinXP at home to the P-II laptop my mother has from work, once Firebird loads (which does take an extra couple seconds compared to IE) it's just as fast if not faster than IE.. Where are you noticing "sluggishness?"

And with all the handy extensions (http://texturizer.net/firebird/) available I've been quite happy using 0.6 as my default browser on every computer I use. (Except macs. Safari wins hands down, even over Camino.)