Well, I can't speak of IE9, as I haven't used it enough. And I don't care about it. But I don't use IE due to bad history - you should be glad that the World Wide Web survived, grew and evolved despite the existence of Internet Explorer. And even then, IE has been a hindrance, maybe not a significant one but a hindrance nonetheless to the improvement of the WWW. Furthermore, IE has historically allowed very few freedoms - remove it and something breaks. Moreover, just its presence on the system is a security issue and could be a target even if you didn't use the browser. Well, keeping it up to date is a solution but it's getting ridiculous - constantly applying patches to something you don't even use. And then there is the fact that IE is so slow to go with changes and improvements that have been out there for so much time. It almost seems that IE is reluctant to be better.
I myself use Firefox. I love the ability to customise it. And Open Source is a plus. Now, I may be talking out of my ass here, but I don't think IE offers a good selection of addons. Just googled "ie addons" and nothing in the top 3 pages was about getting them - just general information about what addons are and such, I didn't look further down, maybe there was an addon repository/collection or something there but the fact that it's not in the top 3 speaks loads. Anyway, back to FF (and actually third party browsers in general) - it's faster to adapt to the Web, it's faster to implement the standards, it's faster to fix security issues. More flexible, more adaptable, faster developing - I'd say those are the signs of a better browser.
I don't know what you use your browser for but either Firefox or Chrome (or Chromium, if you wish) are all good. I haven't used Opera much but I would also recommend it. Safari is...well, it has some bad history too but it's not such a bad browser. From what I've heard, though, it doesn't have a huge advantage having it on a non-Mac. Well, I actually like WebKit (what's in the core of Safari) but Chrome also uses it, so whatever.
Firefox offers huge customizability, thousands of addons (plus, has FireFTP - the best FTP client I've used so far. And it's an addon for a browser), and just other options you can tweak. If you want to do work with the browser, FF probably has the tools for it - Firebug is (I think) still the best web developer help out there.
Chrome cuts down on the customisation but it makes it up in speed - speed of use and speed of browsing. FF tends to be a bit, well, let's say it straight, somewhat bloated at times. Chrome is trimmed down, fast and it still has a good number of addons. It's pretty sweet, it's my "backup" browser.
Opera...well, I don't really know much, but from what I do, a significant number of the UI innovations come from it and are adapted to the other browsers (tabbed browsing, I believe comes from there. Now Opera supports tabs within tabs). Also, addons. They are there, I don't know how many but I am led to believe they are enough.