I was very pleased to read an article from Alex@Google that describes how they have decided to develop the new gmail mobile web interface.
There are at least two reasons why I liked this article, one is that, as Alex mentions, the team originally developed a J2ME application (that I used quite a bit on my old Sony Ericsson W810i) and then decided they needed a web application to serve slightly different needs (and probably slightly different users). The second reason is that it seems like if you don’t create an application for the App Store you are going to fail, while Alex explains quite a few reasons why developing a web site was better than a native application.
Bottom line is, of course, that users get multiple options and an opportunity to choose what suits them best.
I think the article is well worth 10 minutes of your life, if you still haven’t read it, hurry up to check HTML5 and WebKit pave the way for mobile web applications.