The E71x is expected to be available in the next few weeks.
Here's the extract from the AT&T press release:
The thinnest smartphone on the market, the Nokia E71x, will be available in the coming weeks for $99.99(1) and features a black steel finish and award-winning design. The Nokia smartphone, based on S60 on Symbian OS(TM) offers the Wi-Fi and the flexibility of many Symbian-based applications, in addition to AT&T's most popular services, including AT&T Navigator. The Nokia E71x is just 10 millimeters thin and will turn heads when you text friends, or check your corporate or personal email. Customers can learn more at http://www.att.com/nokiaE71x.
You can read our review on the Nokia E71 here.
More information is available on AT&T's E71x page.
Via Unwired and Symbian-Guru.