Based on Net Application Report, iPhone browser's marketshare is about 0.1% now. That is only 6-month after it was release, while MS CE/Mobile is only 0.06% after more than 10-year effort.

For me, the bowser is better than any other mobile device, is good to have, but can not replace my laptop or desktop. But email is a different story. I am using iPhone to access my email even when I am at office/home.