As a Microcell user in one of the pilot markets, I can tell you this device is not yet ready for prime time. There's still too many issues with garbled calls, random loss of connectivity and a few other minor issues (problems establishing the IPSEC tunnel to AT&T, GPS issues). Most problem escalation calls that I've had go straight to the engineering team (which is nice for us), but I don't think AT&T can handle the customer support until those issues are ironed out.
Once they get the issues worked out this will be a great device.