I'm not sure about the general public but for some reason after my somewhat recent upgrade to OSX Snow Leopard - Flash on Firefox just isn't working. In my usual browsing, my Firefox app hangs probably 2-3 times per day, on average. This is all due to Flash elements loading in the page. I've tirelessly searched online for answers, only to find endless threads commending Snow Leopard on being leaps and bounds ahead of its predecessors in terms of speed and reliability. Unfortunately this has not been my experience.
Luckily, I've found a solution. Maybe not one you would expect..
I love Firefox. I'll be the first to recommend Firefox to my friends, family, clients, and co-workers due to its speed, standards compliance, and overall great extension support. When it comes to building a web site, nothing can beat the powerful tools available such as Firebug, Colorzilla, and the Web Developer Toolbar, to name a few. It is in fact the one and only browser I turn to for html and css web development. That being said, I have now almost completely switched over to Safari for my day to day personal browsing.
Don't get me wrong I still enjoy working with Firefox, but for simple no frills browsing on a Mac, Safari is faster. Period.
I now see pages load instantly. Flash advertisements used to add 2-3 seconds to a page's load time. I now see the content immediately without waiting for the flash to load. Maybe this has something to do with the order in which the browsers load certain content, I'm not sure. Whatever the case, over the course of a day it saves me a significant amount of time.
Safari may not be for everyone, but for you diehard Firefox users who might not have considered it before, give it a try. It may just give you the little bump in performance you were looking for.