Try using either Safari or the WebKit nightly build (www.webkit.org). Both are much faster than Firefox, I've found, on the Mac. Firefox isn't nearly as fast on the Mac as it is on Windows, sadly. Another really fast option for Mac OS X is the latest Opera, which is worth a try if you haven't tried the 9.x builds. I've never noticed any sluggishness on the Blacktree wiki site. Also, try using Google for Quicksilver info. There are more guys out there with tips and tricks for QS than you can shake a stick at... mostly motivated by the poor Blacktree documentation (although it's much better today than it was a year ago).