I posted the original suggestion on UserVoice, and I later developed a native iPhone application (as discussed herehere, the screenshots are from an older version).
First of all, for iPhone users, there's a huge difference between a mobile-optimized website and a native app. Therefore, even if there was a mobile-optimized version, I would still continue developing the native app.
Now, back to reality. The RSS feeds don't provide enough information (votes, views, etc.), and therefore the app parses the XHTML, which is quite fragile. Given the time it takes for Apple to approve new versions and bug fixes, even seemingly small changes in the markup could cause the app to stop functioning for weeks, and this is precisely why I haven't released the application yet.
That being said, if an official API is ever released, we can have a fully functional app in a matter of weeks.
As I've said before, the app will of course be completely free, and I'm willing to publish the code under GPL.