I've always found Opera to be innovative and easy to use. They seem to get their default styling right too.

Personally I use Firefox as my main browser but that's because their web dev tools won me over first and now I'm entrenched.

Sync between a very good mobile and a desktop browser would seem to be a good reason - if their Android browser didn't force close on me so much I'd be tempted towards using Opera on the desktop for non-dev stuff.