As a longtime Windows Mobile user, I was obviously ready to ditch the Internet Explorer 6 browser as soon as I used it. It's nice to see that it's more compatible with flash and other web elements, but it still sucks system resources (more now, if possible) and still has a terrible browsing interface.
I went with the Opera 9.7 Beta initially as my default browser, but now I'm using the
Iris Browser for Windows Mobile, by Torch Mobile. It's WebKit-based, does multiple tabs, and is quite responsive. It's WAY more compatible with websites than Opera is, even does AJAX really quickly and nicely (for instance, upvoting on reddit.com worked flawlessly). I'm pretty impressed, and would recommend Iris over Opera.