I don't own an Apple mobile device, but Opera Mini has always been a fixture on my Windows Mobile devices for the past couple years. When I found out Opera Mini 5 was going to have a native WM version, I was overjoyed (no more waiting for the JVM to start)
As far as my opinions of the browser: No, Opera Mini doesn't have Javascript, Flash, Java, or HTML5 support, but that's not critical. Why? Simple: when I'm browsing on the go, that content doesn't matter. I want the text, images, and a proper layout, and I want it quickly. I've used full browsers on Windows Mobile before (Opera Mobile, IE Mobile 6, Iris Browser) and none of them render fast enough. Furthermore, Flash is terrible on mobile devices - slow and battery consuming.
A quick speed test to prove my point: My favorite web comic (
Air Force Blues) on a 5Mbit Wifi connection takes roughly 15 seconds to render on Iris Browser 1.1.9*, but only 2 seconds through Opera Mini 5. Sure, not having JS means I get to miss out on the comments below the comics, but that's a small price to pay.
So is Opera Mini a full browser? No. I do think that it is a good general purpose mobile browser, especially if you're in a country where the Telecom companies all have caps on mobile data (I'm looking squarely in your direction, Canada).
* Iris Browser is based on Webkit, and uses SquirrelFish Extreme for JS. It was probably one of the best full browsers for WM before RIM bought out Torch Mobile and they stopped WM development and distribution.