Google has a new 'tier' of Nexus 7 tablets that can use AT&T or T-mobile (or any SIM-card-using) data networks, and they're just $50 more than their WiFi-only siblings. They're sold out in the Play Store right now, but I imagine they'll be restocking for the holidays.
Google Play via
Wired.
I won't have the funds to buy myself a $300 Xmas present, but it's one of the more tempting tabs I've seen in the latest crop. Mobile data somewhat balances the lack of a microSD slot, and 32GB is at least adequate, anyway.