I have to press 5 buttons on the remote to watch TV

tcneon -
The only reason I can think of that it did not work is that you did not yet program the aux button for the HT. You did do that step??
After programming you would always remain in the att mode. The power button press would send three different IRs while in the att mode.

How do you have your volume control programmed?

I do favor Harmony remotes if you feel you cannot get the U_verse remote working. Newegg.com usually has a refurb remote for less than $18 including shipping.

I have recommended to many people that were unable to find codes to support their devices with the U-verse remote that they get a Logitech Harmony remote.
 
Many of those people feel they do not want to, or should not have to, spend their own money for a remote.
 
Others, have a very complex setup and are willing to spend their money to maximize their viewing experience.

The U-verse remote is effective for some subset of basic control functions on the most popular equipment, The Harmony provides more efficient control of complex setups across a broader range of equipment.

Until sometime in 2011 the Harmony only offered expensive models (over $100). In 2011 they introduced the model 300 ($30) followed by the model 200 ($20). These only support one activity (Not many for a Harmony, but same as U-verse) - Watch TV.
 
This writeup shows that, even though the basic descriptions sound the same, there are functional advantages to the Harmony. The question is - Is it worth spending $$ for the Harmony.

Basic Similarity (Logitech Harmony Model 300 vs. U-verse remote) -
 
Both can control four devices (STB, TV, DVD, Aux) under one activity - Watch TV.

Logitech Harmony Model 300 -
 
Must be able to do something no other remote can do to convince you to spend $30 to buy it so Logitech can make a profit.
 
Monster library of supported devices built on budget for expensive remotes (amazing how libraries grow over the years).

You can predetermine support of make & model via web site (http://myremotesetup.com/EasyZapper/New/Main.asp?WebProcessAction=Start&ReturnUrl=%2FEasyZapper%2F%2E%2FNew%2FProcSpice%2Flanding%2Easp&ClassId=PrSpice%2EProcSpice&RelativePath=ProcSpice%2F).

Since device support is defined in detail, a Logitech customer service rep (CSR) can help with any problems. When anything new comes out it can be added to your existing remote via download.
 
To program - Enter device make model in computer  based wizard. When device is supported, all functions are supported. IR signals can be learned from device remote.
 
IR/function/button  map - You can map any button to any function. You can pick buttons based on your preference, instead of someone else's. Logitech can add any new IR code format to function mapping via download. CSR can download changes that affect only you,
 
Watch TV button - Turns on/off programmed devices. Sets correct input. Ability to sequence devices and introduce delay between devices.
 
Change from Watch TV mode to individual device control with one button push and vice-versa. Same volume/mute buttons will affect different devices (STB, TV, HT) depending on device selected and the one user selected for the Watch TV activity. Note that the U-verse phantom mute can be un-muted with four logical button pushes - device mode, STB, mute, return to watch TV mode.
 
Able to buy more advanced remotes for more money - Each step up adds more devices, more activities(e.g. Watch OTA, Watch DVD, Watch TV with HT sound), more display (LCD screen) of functions & recharge-ablity .

Multiple activities appears to be a concept unique to the Logitech Harmony. It allows the same buttons to be programmed to different sets of functions/devices based on what the viewer is watching (i.e. an activity). The button map is unique to the activity. It can be as similar or different between activities/devices as you need it to be. It is especially valuable for complex setups and/or people with only basic knowledge of the operation of the remote.
 
*****************************************************************************************************
 
U-verse  remote is provided free to watch U-verse TV. Support for some functions on some other devices is included so that it can be called "universal". But there is no business driver to spend money to assure full support of all functions on all possible devices .
 
Limited library of supported devices. Vague lists by type/mfgr. No model detail. No definitive/comprehensive list of codes. No "not supported" statement. If support is not accomplished, there is no way to find out if it should be supported until you find that the remote works for you. Since device support is not defined in detail customer service rep cannot help with problems.
 
To program- Enter an arbitrary code that may be difficult (or impossible) to determine or step through every possible entry using the search method. Possibly finding some partially supported sets along the way.  No IR learning.
 
IR/function/button  map - Button/IR map cannot change (need new physical remote). IR/function map can only change if U-verse globally changes STB software. No ability to provide individual tuning.
 
Watch TV (ATT/power) -  Turns on/off programmed devices. Does not set input. No ability to sequence devices or introduce delay.
 
Default mode of operation is Watch TV (Channel change on STB, Volume on TV, Power up STB/TV). To vary operation requires reprogramming with more arbitrary codes applied to individual functions. No clear distinction between Watch TV and individual device control (i.e. It is difficult to change operation between Watch TV and controlling individual services by programming with codes.)

To clear phantom mute - att/ok - 955 - att - enter - mute - att/ok - 955 - tv - enter. 12 button pushes, where two are two finger. If you can remember how to do it.
 
Point anywhere remote is extra cost upgrade - provides RF (with STB pairing) and learning IR.