It sucks if you have a fast connexion too, because then your CPU and RAM suffer instead. And as you add addons to rectify the many offending web pages, then the performance penalty of those quickly equal to that of crappy JS. I was so happy with Xombrero as my browser, but it's stagnant and insecure now. I do like my Firefox but with all the blocking addons it's slow, and without them it's slower (not that it's its fault).