Somewhere during the IE8 beta, I did a similar thing. IE8 at the time was horrible: slow, buggy, crashed a lot, and I figured that if things didn't improve before the final release I needed a different browser. So I evaluated different browsers at the time.
This means that the below applies to whatever version of those browsers was available in early 2009, not the current version.
I don't particularly like Firefox's UI, and its update process is (or was at the time) poorly suited to standard user accounts. Chrome's UI, while sleek, didn't fit my workflow at all. I use my favourites a lot, and Chrome's UI just isn't designed with that
in mind. I also didn't like the background updater process constantly running, and the lack of an RSS reader. Opera I liked most, but it didn't render Channel 9 correctly (same issue that Herbie described) which wasn't acceptable for me.
Fortunately, IE8 cleaned up its act before final release so I stuck with that. It's also the only browser (as far as I'm aware) where I can subscribe to an RSS feed and have it automatically show up in Outlook, which I rather like.