Just for your info, Sky have just recruited my friend as a project manager to start the build on their new 600 HD channel playout system. Currently a HD channel will use the same bandwidth as 4 normal channels and if it is transmitting Dolby 7.1 it uses up 8 times more bandwidth than a normal SD channel, hence they are only using it on certain channels and certain shows. Big budget shows such as Lost, 24, CSI, and in some respect music videos/live performances are shooting in HD however they are only transmitted in this country as a high res SD channel as said before. They look a lot better though due to the contrast and colour definition that you get from a HD camera and post production suite.
Personally i would not be buying anything yet anyway and wait for Blueray and HD-DVD to have their battle first, before going down the HDTV route. Also prices will be going down a lot come August.
ALSO - August will see the release of a PS3 game, which will spark a reduction in price of the PS3 so i would wait until then to buy one.