@hdtvi: The built in iOS mail app has hooks into various email services like Gmail, Yahoo Mail, and Exchange. A couple benefits:
* One unified inbox for all your mail
* Mail can be accessed offline
* Attachments can be opened and edited if you have the appropriate helper apps.
Non-web syncing occurs if you have any modern mail server. For example, a lot of businesses use Microsoft Exchange. I can receive/read/send emails on my iPhone. These actions are transmitted back to the server and sent to my iPad and Microsoft Outlook.
@scampbell: What about syncing of calendars? I know executives at several companies I work with that would go ballistic if they had to go to a web page to see their calendar.