Yeah, HDBaseT products have been out for a while now, even before the standard was published. Crestron is by far the biggest name is digital transport technology in the AV market. Yes, there's a large demand for it. A Crestron rep said that their DM Line was about 40% of their sales for last year, would would amount to roughly $200M. This type of technology is used in the commecial AV market, not really broadcasting, and not prosumer. More for your college and university settings, corporate spaces, auditoriums, etc. These are often part of a larger AV system and not just a transmitter end and a receiver end. Often these feed larger systems that offer matrix switching and various exotic control aspects. I've installed a school where classrooms had an HDMI/VGA input box and a projector all going to a centralized location in the school. Each room only required two Cat5e runs to the centralized area and that was it. The input box was one and the projector was another.
The reason it's popular is because of the distance limitation of HDMI as mentioned, not to mention that HDMI cables aren't really field termination friendly, and don't fit in conduit. Cat5e is cheap and already pulled throughout most buildings, not to mention everyone knows how to terminate it and has the tools.
Other members who utilize HDBaseT technology include: AMX, Atlona, Extron, Gefen (mentioned in article), Kramer, and Magenta.
The transport standard (not everyone uses all aspects) should fully support everything that's included in the HDMI standard, ethernet, RS232, USB, power upto 100W, and maybe some other stuff I'm missing. Some displays will run on a single Cat5e without an additional power cable. They had one rigged up at Infocomm, I believe the PrimeView PRV42WRCHDBT is the panel. Panasonic has a line of projectors coming out (or recently out) that have HDBaseT jacks directly in the back of them, though of course even if the switch that feeds 100W was easy to get projectors take up way more than that.
Other digital transport technologies include over fiber. This is not standardized like the copper solution, so what each manufacturer includes varies wildly. For example, AMX doesn't support HDCP on their fiber solution (yet). Crestron has a single mode fiber that should transport everything in the copper solution (minus power of course) 7.5 miles. Yeah, Tom doesn't have a whole lot of AV coverage as this stuff's all been out for a while, hopefully our market will get some good attention in the future.