Freesat and Freesat from sky are ALMOST the same, there are a few differences in channels available plus when they do an update of cards you will need to pay Sky approx £20 for a new card, this is normally every 5ish years
http://www.ukfree.tv/allchannels.php gives a nice list of the channels available on each platform
I will be having all free, my TV has built in HD Freesat so will get the HD channels through that, I have the standard Sky plus box so won't get HD through that (OK I lose the + part of it unless I can find away round this) and will have Freeview but watched via the PS3 with a PlayTV thingie
http://www.superfi.co.uk/index.cfm/page/moreinfo.cfm/Product_ID/4515 (assuming I cant get the sky + to carry on recording after my subs finish on the 16th)