OK, so the description says Series 1-4 have been 'newly remastered versions at full 1080p resolution', but let's make one thing clear - THEY WEREN'T SHOT IN HD. They were shot at PAL 576i, so the only way to transfer them to HD is to upscale them to 1080p, as was done with The Next Doctor on The Complete Specials set. So as it is the description to me is just marketing fluff and not actually a fair representation of the first four seasons of New Who.
It's well known that the BBC were in fact offered HD cameras for Series One, but they rejected them because it cost too much to render the visual effects in HD. They only truly started shooting in HD with Planet of the Dead.
I'm not trying to put people off buying this set, so please anyone reading this don't take it the wrong way. All I'm doing is educating those who are expecting to watch the entire of run of Eccleston and Tennant in HD to not be disappointed when they find out it's inferior in quality of Matt Simth's tenure.