I was having stability problems with 5.0 and 5.1b1-3, but 5.1b4 has been rock solid for me. (For those having trouble, you might try emptying the cache, and if that doesn't do it, moving the prefs out temporarily to see if that helps).

5.1b4 can now save pages without downloading them again, fixing my most serious complaint about OmniWeb. I'd still like to see:
- Saving a page or set of pages as an archive (with links that work and images included), a-la iCab.
- An "ask" preference for cookies. Simply disabling them causes some sites to fail to load, making it a pain to correct site-specific prefs.

Overall this is a wonderful browser. A very nice site-specific preference implementation allows one to easily block out ads. The interface is nicely polished and the tech support is excellent.

Worth every penny.