Opera Mini now the number one free download in all 22 App Stores — Engadget.
That said, I agree with John Gruber when he writes on Daring Fireball:
Worst of all: scrolling. The iPhone uses a heuristic when you flick to scroll, such that if your finger is mostly moving up or down (or left or right) it locks you into that dimension when scrolling a view — such as a zoomed-in web page — that could be scrolled in any dimension. The effect is that when you’re zoomed in on a column of text in MobileSafari and flick “up” to scroll down, the view moves straight down, even if your flick gesture was a few degrees off. On Opera Mini, however, scrolling a zoomed-in view moves in exactly the direction of your flick gesture. The result is that scrolling an Opera Mini page feels like sliding a sheet of ice on an oil slick.