Hi Ray
I would not say there are huge advantages at present. In fact there are disadvantages in that Channel 4 (and +1, More 4 and E4) and Five (and Five Life and Five US) are not currently Free To Air as they are on DVB-T. There is strong speculation that Channel 4 will go Free To Air in the spring as Film 4 and Film 4+1 are already Free To Air on satellite.
You will find a full list of FTA channels at:
http://www.astra2d.com/sky-fta.htm
I have noticed on the Virgin Media box I received when I moved (as I changed to the 2 for £20 package (although you get 3 for some reason)), some of the channels that are not available (i.e. you have to pay for) are Free To Air on satellite (e.g. Classic FM TV).
An advantage that there will be is that BBC HD is already on FTA satellite and ITV HD is expected to launch there. How much of an advantage this is depneds on when you expect to get an HD TV.
I am hoping to get satellite installed at my new house to have the best of both worlds (DVB-T and DVB-S)
Mew