While I agree about the great work that’s been going on with Opera Mini, its still the most part a browser that people have to download to their phone, which sadly can present a large enough roadblock for many. The majority of people don’t even know which browser they have on their phone, let alone how to load an alternative one on it.

Also one can’t underestimate the fact that, from a developer’s point of view, the iPhone-toting demographic is a VERY attractive one to build for (and that’s only going to grow).

That’s not to say that Symbian, Windows, etc. won’t continue to be big. I just think that Apple’s strategy is now looking the most promising in terms of moving mobile application development/adoption forward in a similar way that they changed the game in terms of what people have come to expect from their phones in terms of user interface design.

You make a good point that in theory web apps are 100% cross platform and therefore can be used on any mobile device. While for many apps this is true, we also see specific browser targeting by developers. The most prominent of this is the iPhone where developers not only specifically target Safari but also mimic the look and feel of the Apple operating system. With all of the great work that Opera is doing on their mobile browser, I predict that developers will also start taking advantage of features specific to that platform.