Says Google's blog:
Today we're happy to announce a new and improved experience when you access Gmail and Calendar through the browser of your iPhone and Android-powered devices. What's new? For Gmail, we've improved the user interface to make it easier to message on the go, and we've introduced "Floaty Bar," which makes sure common actions such as archive and delete are only a click away (check out the video tour below). You can also start the application, compose mail, and open recently read messages even when you're offline. With the new Calendar, you can edit or respond to an event and, like Gmail, the app is accessible even without a network connection. To quickly navigate between Gmail, Calendar, and other mobile applications, you can use the classic links that now always appear across the top of the screen. The "more" menu provides easy access to the full list of applications. To read more about what's new, take a look at the Gmail and Calendar posts on the Mobile blog.
Google claims they're focusing on WebApps over native apps because they're faster to iterate which makes sense, especially if they want to leverage their work across all WebKit mobile devices (iPhone, Android, and soon Palm Pre). Still, we have to ask...
Where's our native push Gmail?!