Technically speaking? I have no clue, the way it handles the pages I suppose, but it's really fast in comparison to the stock browser on my Eris. Dolphin was only a little faster and the first version of it I used (can't remember what revision number(s)) was the best, then they kept adding stuff to it and changing the interfaces more than monthly. Got annoying fast.
The home page on Opera is nice, you get 9 little bookmark, similar to Safari's (desktop) Top Sites or Chrome's version of it too. I don't use Opera on my PCs, just Chrome so I don't know much about how it's better, only had it for about an hour.
In the settings you can turn off or on the "Mobile" setting and it will enable or disable the Mobile Websites. Some sites render funky, like Roosterteeth.com renders the Horizontal Menu horribly, jumbles up the links and some buttons don't display properly. AC.com renders pretty well and it seems faster in 3G than the default browser was on WiFi. Just different is all, not too bad though for a beta.
Also a long press doesn't pop up the standard options menu, it's re-skinned for Opera and clicking a dropdown menu brings up a similar list to what the long-press menu is.