If you've been using the web-based version of Gmail on the iPad, you may have noticed that yesterday you started to have a big, full screen compose window for writing messages. Instead of splitting the screen between your inbox and the compose view, we updated the interface to hide the inbox messages on the side and make more of the text you're working on visible at once.
To try out Gmail on the iPad, just go to gmail.com in Safari. Please note that the new interface is only available in US English for now.
For more info, check out this post on the Mobile blog.