It's not a completely new browser as it's page renderer is WebKit (as used by Apple).
So far, I've been pretty impressed. Its general UI, particularly handling of tabs, is way ahead of any of the other browsers I've used (though I've not significantly used Opera, so I don't know how this compares).
However, it's clearly still a Beta, and missing many features that I'd consider essential for it to be my main browser. For example, there seems to be very little control over scripting or plugins for particular pages.