Better back and forward navigation
In general but especially when mis-clicking a link in most Android browsers going back is imo a real torture. Everything on the previous page -ads, cookies, scripts, plugins and whatnot- is reloaded from scratch this takes time and data. Reloading from cache like ie UC browser does would save both.
Opera adds an extra bit by nesting the history so trying to go back 4 or 5 steps can be a real puzzle.
Opera (even the mobile Chromium-based one) used to have fast back then it stopped working / feature has been phasen out without announcement. You also used to be able to hold the back button to show tab history.