It's interesting, I was having a chat with Ian regarding my recent switch to the Firebird browser, which is developed by Mozilla. And the day after this, I check out Patrick's site today, and it seems that he has discovered Firebird as well.
I really had never installed another browser other then Internet Explorer before, but since I've been reading 'Designing For Web Standards' my eyes have been opened up to a whole new area of web development. I downloaded Firebird, and immediately was impressed by the features and the smoothness of it's operation. So as of right now, Firebird is now my default browser, and I'm very happy so far.
A little side note, since this page became XHTML validated, Firebird now accounts for almost 9% of my hits, where as before it was under 1%. A couple of hits from a Dreamcast browser as well. I wonder how it looked in that.