Google’s released a new mobile interface to Google Apps that is a much better way to access your stuff from the iPhone. You can use this from any browser (I think), but it’s a rockstar on the iPhone.
The upgrades? Easy access to your calendar. Easy access to Google Docs. Notebook. Reader. News.
Point your Safari browser to http://www.google.com/m/a/<your domain> and have fun.
Best practice: I add a home page icon that points to http://www.google.com/m/a/<my domain>#gmail to get to my e-mail in one click.