Last week AT&T unveiled their new 18Mbps U-Verse "Max" tier, and users in our U-Verse forum are putting the new offering through its paces. As we discussed last week, the new tier is aimed at all VDSL customers -- even those with connections that are distance-limited at 25Mbps for both TV and data bandwidth. That means that not only does AT&T need to get rather fancy with compression, but they had to introduce QoS that effectively adjusts to TV bandwidth demands on the fly. In other words, the 18Mbps tier may become considerably less than 18Mbps -- depending on how many HD or SD sets are currently on in your house.

While that sounds like trouble, initial user reports seem promising. Users say the upgrade for existing customers is fairly painless, and customers on a 25Mbps downstream and 2Mbps upstream VDSL profile aren't seeing profile changes.

As for speeds, "tests are around 17250/1450," one new user e-mails me. "When 2HD+2SD streams are in use it drops to 12-13mbps," he says. "When just dual HD streams are in use, it hovers around 15, which isn't too bad." At the moment it looks like the HD compression is topping out at around 5.5-5.8mbps per stream, but that can lower depending on how much line activity is occurring (that's why AT&T recently changed their TOS).

With all this HD rate and prioritization going on, you'd think you'd see a significant hit on HD quality, but users so far say that isn't the case. Or, at least the compression and artifacting is no worse than what they're seeing from local cable operators. "There are some obvious flaws in the picture due to the compression but it's nowhere near as bad as the mess we now get from Time Warner since they've squeezed in 11 new HD channels without SDV," user djrobx says.

According to some users at the official AT&T forums, when customers call in to get the $65 tier (as opposed to upgrading online), AT&T's offering a $10 discount for six months. Some of our users also say that calling in resulted in them getting $20 AT&T VISA gift cards, a promotion AT&T is running throughout Novemeber for users who upgrade.