Our U-Verse internet has continued to be rock-solid (keeping fingers crossed) but during the month we've used it so far, there have been a few minor issues we have come across, which I will document here for Google and posterity. Two of these have easy workarounds, and the other two will not really matter to most people, but might to you, if you are a special flower....so read on....
First, the two issues that have workarounds:
1. The U-Verse gateway's DNS doesn't like Apple computers.
The workaround for this is easy. If you use a Mac, simply set your DNS to use OpenDNS (or if you have a bunch of Macs, you can do this in the router)
2. U-Verse's head end blocks outbound traffic on port 25 for non AT&T email accounts.
This is the port that is used by most mail programs when they send outbound email. This isn't something you can change locally in your router, but luckily AT&T will unblock it if you ask them. We were able to get this done in 5 minutes via their online chat support, but other people have had to call in to tier 2 technical support.
And second, the two issues which might be deal-killers for some folks:
3. U-Verse utilizes interleaving for their data transmission.
Interleaving is a method of transmitting data in non-sequential chunks to increase overall performance. This is good for things like TV, but it has a side-effect with internet...slightly longer ping times, up to 20 milliseconds or more. This doesn't matter to most people....unless you are an online gamer. Online gaming relies on very fast response times from the servers, and the added overhead of U-Verse's interleaving may degrade game performance in some games. This isn't a "100% for sure" thing...it depends on the game and the server, but it is certainly something that should be at "yellow alert" for any gamers considering U-Verse. Take advantage of the 1-month free trial and test with all your favorite games.
4. There's no way to get pure unrouted internet access to a local device.
U-Verse allows you to set up a DMZ, which for an individual PC will allow in all internet traffic. This is considered dangerous and only experienced folks who know what they are doing should use the DMZ. However, some physical devices, such as hardware VPN routers and firewalls do not like being in a DMZ; they prefer pure, unrouted "raw" public connections to the internet. U-Verse's residential gateway cannot be placed into the "bridge" mode that is required to do this, so if you need this functionality, make sure you test your devices with U-Verse during the free trial period to make sure they work.