It's pretty sweet, much easier to use than version 3. I have been using it for a while and now that beta 2 just came out it's even better! For those who haven't used version 4 yet there are some pretty sweet features:
Full screen view - view it like it's supposed to be viewed
Zooming - kind of how the iPhone's browser works
LANDSCAPE MODE - better suited to view web pages in this mode - plus it looks sweet while you're using your phone sideways (unless its a flip phone heh)
Mouse cursor - so you can select things on the page easier, its convenient.
Best of all, it's free! Go check it out at
http://www.operamini.com/