My heart is firmly set on Opera. Yeah you could call me one of the devotees who actually use Opera, but for good reasons:
1. Its Fast
2. Its not bloated (Look at the memory usage of FF2 and IE7)
3. Best at sticking to Standards
the list goes on...
I use it everyday, and 99.99% of websites I visit work fine in it. The only websites I come across that don't work are normally microsoft websites e.g: Windows Update, Windows Live and Windows Live spaces. And I have ie6 on backup for those.