I've tried _all_ the other Mac browsers, most for several days each, and I always come back to OmniWeb. It simply has features that the others don't have or that require adding with plug-ins of variable quality (which then go obsolete when the browser itself is updated).
Why do I keep trying other browsers if I love OmniWeb so much? Memory leaks. I've tested the memory use of most of the Mac browsers and those that use WebKit all leak badly. OmniWeb seems to add on to this bad situation, using more memory than Safari. The more memory my computer has, the more memory OmniWeb uses. I have 2 GB and OmniWeb, over a couple of days, depending on usage, will typically hit 450 MB of Real Memory used, as reported by Activity Monitor. I can watch memory use grow as certain functions and certain pages are loaded; when the pages are closed, memory is not released or is only partially released.
(Some people explain that the numbers reported by Activity Monitor require expert interpretation, saying e.g. that the memory required by certain frameworks is reported as all belonging to each of the applications that is using the framework. So what. That doesn't explain 450 MB. Furthermore, I can quit OmniWeb and relaunch it--the exact same state is restored when you relaunch, one of OmniWeb's nicest features--and the memory used is hundreds of MB less. So much for the "you don't understand Activity Monitor" theory.)
Anyway, the cure for this is to relaunch OmniWeb from time to time. Aggravating to be sure, especially if you were logged into one or more web sites since you'll have to log in again. But the saving grace, like I said above, is that OmniWeb exactly restores the complete state of the browser upon relaunch (related to one of its coolest features, saved workspaces).
All browsers in the history of the universe have leaked memory. However, I have used the beta 3 version of Firefox and it isn't too bad--it leaks much slower and seems to not hit sky-high memory use like most of the others. But adding and maintaining plug-ins to make a poor approximation to OmiWeb's features, and then operating with only a subset, is more work for me than relaunching OmniWeb from time to time.
The support from the developers is top notch, always resulting in a quick personal reply by e-mail. Crashes are extremely rare but when they do happen the cost is slight because, once again, relaunching brings you right back where you were. $15 for the top browser is a trivial amount (I think I paid $30 several years ago--not sure).