You can set up the email program to get your ATT mail--I used mine with cox dot net.
I recommend the "K9" mail client over the default mail client, by the way--it offers more options and flexibility. K9 is free in the Android Marketplace.
I did import my contacts into Google, since I had to set up a Google account to use the phone. The Google contacts work in the mail client, including K9, regardless of the mail server I'm pointing at. I don't Gmail, as a matter of principle. They know enough about me already; I don't need to volunteer to tell them more.
I use the Google calendar, so I can't help with the calendar question.
For documents, I sprang the six or seven bucks for the Documents To Go application, because it works flawlessly with MS formats (I'm not a big fan of MS Office, but one does what one has to do to earn a buck) and it's not Google Docs.
I have my own cloud; I'm not interested in using someone else's.
I used Docs To Go with my T-Mobile Dash and was very happy with it.