4G, up to now, is the mythical double rainbow that AT&T just can't seem to find. While other carriers are moving to a 4G standard, AT&T hasn't quite grasped the new technology, meaning that your Apple devices will be stuck in 3G land if you are stuck with AT&T.
There is a solution though, and it comes in a cute little, Magic Mouse-like package. The iSpot, from Clearwire, is a 4G hotspot that connects up to 8 Apple devices (the device is configured to filter based on MAC address, so only Apple devices are allowed) to the 4G network via WiFi. You do have to be in a Clearwire area for it to work well, but if you are, you'll get blinding 4G speeds that only space men have witnessed.
Unfortunately, unlike the PC version of the same product, the iSpot is unable to fall back to the 3G network if you aren't in 4G range. So if you happen to live in the Phoenix, AZ metro area like myself, you are out of luck, but next time you go to Amarillo, TX, you're golden. Needless to say, the coverage is spotty.
Check out the Clearwire website for pricing details, and that wonderful coverage map.
Update: Just for clarification, the iSpot's (incredibly cheap) service plan is $25 and can only be used with iOS devices. Ars Technica reports that "the iSpot can't be used to share a connection with a laptop or another non-iOS device unless a Clear rep unlocks it and bumps the service fee to the standard $40 monthly CLEAR Spot 4G plan."