Hi Unfortunately the larger the set the lower quality of the picture also the store is most likely hooked to the cable company in your area that also give a much better picture ,all tho direct TV has come along way in the past its quality just isn't there I have a friend who has Dtv and his pic is perfect but his next door neighbors is poor all depends on were you are , I also have a 42 inch HDLCD and a 19 inch HDlcd the 19 inch lcd has a much better pic

The picture on your Samsung should be fantastic.

Is your ATT box an HDTV box? If not, replace it with one that is.

If so, make sure that the box is set up to actually output HD. Make sure that you are using an HDMI cable to interface the box with the TV.

I have run across many homes where the owner had an HDTV, hooked to an HD cable or satellite box, had subscribed to an HD service, and wasn't actually seeing HD because the box was set to standard output and not HD output.

The box is an HDTV box. Not sure about the cable as the AT&T guy gave it to us to see if we could get a better picture with the last Samsung. My husband likes to think everything is OK and argues to no end but I called the satellite people last night and it was a matter of pushing a button on the remote to get the satellite to work! (Old folks here). I don't know about how to set the HD box. It must be just a matter of reading the book (if we could understand it).

The picture just isn't what I would expect especially when the old bedroom TV on digital is getting a much better picture. Where do I look on the HD box or is it on the TV menu? Thanks.

One way to try to locate the problem: Buy or borrow a Sony BDP-BX1 (includes HDMI cable) Blu-Ray type DVD player and a few discs if necessary. If it gives you the quality picture you were expecting, then your sat feed, equipment/setup, or dish location is suspect.

Maybe the best bet is to call the ATT service people, explain the issues, and have them come check everything over.

If it's standard definition, the picture isn't going to be near as good as a HD picture.
Here's a web site for HDTV. There may be a forum for the model set you have.

Here is a link that might be useful: AVS Forum