i'm familiar with the quick launch" setting, but Firefox (on a PC) launches pretty slowly whether quick launch is s enabled or not. once it gets up and running (on Windows or Mac), i think performance is acceptably quick, and it's even an improvement from the previous 0.7 version (Firebird). Safari is a close second, but Firefox is so tweakable that i can get it to do exactly what i need, with extensions or with my own preference hacking. i use Firefox exclusively on Windows, Mac, and Linux.
most of the perceived slowness of the Mozilla suite comes from the fact that they wrote their own cross-platform APIs. this is both the curse and saving grace of all current Mozilla-spawned applications - the fact that it even runs on platforms other than Windows is attributable to this, but it also has to carry around a lot of cross-platform code.
that being said, there are many parts of the Mozilla suite and the XUL programming language that favor the Windows APIs, and the whole suite is still noticeably faster on Windows than on the Mac. Phoenix/Firebird/Firefox weren't even available for the Mac up until 0.6 unless you compiled your own version from the nightly trunks. while there were other reasons for doing the research the Mozilla team did and coming up with their own APIs and XUL, i'm sure much of the drive to get the project going stemmed from an urge to unseat IE as the vehicle of choice for Windows web users.
the tip recommended above - locking the Safari cache folder - is a good one. that's what i was going to recommend at first, but i wasn't at my Mac and didn't remember if Safari had a cache-setting feature. for the thread-starter's reference, the site is actually
www.macosxhints.com, not osxhints.com