1. Adblock.
2. Flashblock.
3. Simplicity.
4. The only difference on any machine is that it's edit->preferences, because of some idiot who loved Netscape.
5. It doesn't need patching every two weeks, and the overwhelming amount of holes found were found and patched before they could be exploited.
6. Half of the OS doesn't use it.
7. It doesn't have that crazy Opera interface.
8. I can easily remove plugins, like Adobe Reader, Quicktime, WMP, etc..
9. Spellbound is nice, too.
My biggest complaint is that they seem to have every other release be great. 1.0.5, I experienced my first crash since a 0.9. It was slower, and a memory hog. Now, at 1.0.6, I don't even have the urge to use a Moox build, and it hasn't crashed once, nor used up all my RAM. All I want now is columns in bookmarks.
I'd switch to Opera, and maybe even pay for it, if they had an interface like FF.