Okay...I'm very new here and found this thread (I just had U-verse installed in place of Comcast Monday of this week, so two days later this is my impressions)...and I wanted to add a couple things:

1)  I have four (4) HD displays (DLP projector in home theater basement on 88" screen; LCD projector in family room on 80" screen; 37" LCD display in Master Bedroom; 32" LCD Display in daughters bedroom - gone for college most of year...so normally it is just me and my wife in the house most of the year.)
2)  I signed up for U-verse off of Comcast...the single HD feed is currently not a huge issue because I refused to pay for anything other than the one STB/DVR from comcast since the monthly rental for an additional box is ridiculously expensive.  Therefore I only had one feed anyway due to the one STB...BUT the ability now to have 3 STB's with no additional fee allowing me to at least watch the one feed on three of my displays depending on where we happen to be is a huge advantage...AND knowing another feed is coming made it a no brainer.  Not to mention the WHDVR is a big advantage when it becomes available.
3) The HD content on my larger screens does seem to be (as best I can describe it) a bit "softer" than what I have been used to.  But it is not bad IMO.  Hopefully they will be able to do a little better in the future with the compression/codecs to make the HD look even sharper on the larger displays/projectors.  On the smaller LCD displays, I think it looks really good and I can't imagine the detail being much better...I have viewed HD DVD on these smaller displays and I have to say U-verse HD holds up pretty well on the 'smaller' displays.
4) Comcast in the PAST may have looked better; however, they were not further compressing their signal to the end user.  BUT, they have started to do this apparently.  Here is a link for you to read and consider.  More and more companies are doing this...therefore the 'disadvantage' some think U-verse has really isn't a disadvantage any more since more and more companies (even cable) have decided to compress the signal...see this link:
http://www.avsforum.com/avs-vb/showthread.php?t=1008271

So I am happy with my decision...as with every service there could be some things better.  But I am getting better value from this than I would be getting from Comcast since I have 3 receivers as opposed to one...a few more channels/options than Comcast...and soon coming additional HD feed and WHDVR.

BTW, previously it was mentioned that about 40% of U-verse subscribers opt for HD...that is very close to HDTV penetration.  I recently read it was at 39% in the US....can't find that link but here is one that estimates it close to that by the end of 2007:
http://parksassociates.blogspot.com/2008/02/hdtv-penetration-and-sales-figures.html

While I'm sure they have improved some I still think LCDs don't handle SD very well.  If you are concerned with SD quality I think plasmas are a much better choice.  You still get the stretch/black bar prolems but I think the quality of the SD picture is much better compared to LCD.

I have an InFocus IN72 that handles HD and SD programing phenomenally. It's a DLP projector, which I am told is better than LCD anyway. Unfortunately it is not native HD, it only upscales, but it does so beautifully. I think it may have some sort of upconverter in it or something, because all SDTV programming looks better than it did on any other TV I have ever owned, even when stretched to 16:9. But you can change the viewing mode to 4:9 if you don't like the stretched image, but you honestly don't need to. There are other models that do native HD, the IN74ex, IN76, IN78 and SP777. I don't know the specifics of any other those models though.

I love HD programming, my TV does 1080p and my Onkyo receiver upscales everything to 1080p life is good!

I have 3 HD LCD TV'x and as far as I am concerned the SD is pretty good and much better than the DIrectv SD I used to have. Just my 2 cents.