HDTV is bill if you like watching high quality images at the best possible resoultion. Things to which HDTV is excellent for are films nature / wildlife progs, some entertainment shows such as Strictly and of course sports shows.
Things which make no difference : news, documentaries, history progs with poor quality old archive film (WW 2etc) cops with cameras(again low quality shaky cameras) , soap operas, comedy shows, YBF ( poor quality camcorder footage) and so on.
There are only a few progs being show at the present and they are repeated weekly, so it'll be a while before there will be more diversity in programming
To view HD you will need either a tv with built in HD receiver such as this from Panasonic
http://www.hdtv-news.co.uk/2008/05/07/panasoni c-first-with-freesat-hdtv/
Otherwise you will need a sat receiver such as Freesat HD or Sky HD (which is a subscription service.)
Humax are currently the only manufacturer offering an HD Freesat recorder for around �280 in Argos
http://www.humaxdigital.com/uk/products/produc t_stb_satellite_foxsathdr.asp
This will need to be installed by a competent person, not really a diy job cost around �60 or so.
The connection to your tv from the Freesat HD box will need to be via HDMI, scart connectors do not have the required bandwidth to display HDTV.
More clear info here
http://www.bbc.co.uk/reception/digitaltv/faq_h d.shtml