I too have noticed the better quality of the SD digital broadcasts, but I am totally against multicasting. One thing to remember here is that this is NOT a market driven thing. These stations were GIVEN free spectrum 50 years ago to operate in the public interest. They were LOANED more free spectrum recently to transition their existing analog broadcasts to HD broadcasts, still to operate in the public interest. Other spectrum users (cellular phones, pagers, etc.) have had to pay dearly for reserved chunks of radio spectrum, TV doesn't as long as they at least pay lipservice to public interest. That's why every TV station has some newsmagazine or some other local features program, although sometimes it is on at 3am.
Of course when the time came to set the standards for digital, the computer people and others outside of the TV biz suddenly thought their interests should be looked after in this new system. The spineless FCC gave in and allowed 18 different formats to be chosen from and now we are all wondering why J6P doesn't get it - it is too complicated. Some of these 18 formats do work well for multicasting of 4 or 5 stations but that is not why we are changing to digital broadcasting, it is for the better quality.
Incedentally, WRAL in Raleigh runs an DTV channel and a SD channel all day every day and they say they can also squeeze in weather if they want to during storms. I don't really have a problem with somehting like that, it could actually be good. Think about the next time there is a storm somewhere in the area, they can put up a little crawl on the bottom saying there is a storm nearby and tune to channel 5-03 to see details. If you don't care you can still watch TV without the annoying Doppler radar and endless speculation about what time storm cell 39-Z would be over some town 50 miles away and heading the other direction.