well I can talckle the first part of your question. HDTV-Ready means that the TV comes with a tuner built in I believe. There aren't to many TV's like that. HDTV Compatible means that you can easilly hook it up to a tuner that you buy seperately. For the most part compatible is prefered so you aren't stuck with a tuner you don't want.
To tackle the DTV, HDTV part you have to understand SDTV first. SDTV (Standard Definition Television) is what most of the US watches which is at a resolution of 480i, and its an Analog signal.
DTV (Digital TV) gets broadcasted . . . well . . . digitally as opposed to an analog signal with resolutions of 480p to 1080i.
HDTV (High Definition Television) is a specific piece of DTV. It uses resolution 720p or 1080i. Basically its the best in DTV. There is a 1080p, but thats only for REALLY REALY REALLY High end stuff that only companies will see for some time to come.
What does the p and the i mean? Well the I = Interlaced. When you look at a TV screen your not really seeing the whole picture. First you see the odd lines, and then u see the even lines. Lets say your tv had 6 lines. First it you would see 1, 3, and 5, and then 2, 4, and 6. It happens SO quickly (thousands of times a second) though that your eyes would never be able to see it, and think that its one whole image.
P = Progreesive. Basically instead of showing you half the image and then the other half, it shows it to you all at once giving you a better image. Your computer your looking at is probably using progressive.
As far as the obsolete part . . . well thats up in the air. New TV's will be coming with firewire, and there is going to be an odd period where some tv's will have a certain connection, and will work with certain equipment, and other tv's will work with other equipment. Only time will tell who wins.
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STOP DVI/HDCP!!!!!
