Useful, but they didn't include Google Apps. No need to deal with an SMTP server, and it's $50/year or free with ads. It's a lot easier to sync calendars and documents across a team if everyone is using Google Apps.
Some businesses like keeping their data internal. There's nothing wrong with running your own SMTP server. Personally, I'm not exactly thrilled with Google's choice to make email into "conversations." Plus, how much control do you have over your data if it's in Google's hands?
Ever heard of Hula?