It lasted 8 days this time around. After using Safari 4 as my main browser for about a week I decided to let it go. Despite applying the tweaks from this post there are still a few things that just isn't working out for me:
1) The setting to force opening of new windows in tabs is a little too "always" for my taste. I want (allowed) pop-ups to pop-up, but links that request a new window to be opened in new tabs. I believe this is the Firefox default and it works great.
2) Blocking pop-up windows is nice, but I'd like the browser to tell me when this happens, so I can elect to view this particular pop-up if I wish,
3) Once you get used to the Awesomebar, all other URL bars are, well, not so awesome.
So, for now I am running Firefox 3.5 rc2! If you have any ideas on how to fix the things above, please let me know and perhaps I'll try out Safari 5.