for Hard drive recorder thingies... I have Sky+ and it's absolutely awesome. Pause live TV while you nip to the loo and you can even rewind live TV assuming it's the channel you've been watching... bets of all is series link, find a program, press the (R) button to record, then the green button and it'll record every episode in the series... Also on sky adverts highlighting programs on sky channels, you can press the green button during the advert and it saves a reminder to watch that program... Truely genius!
as for HDTV... it depends, for regular everyday watching TV it's a complete waste of time (very few channels broadcast in HD at the mo, so you're left with the same pic quality) -If however you play computer games with a HD console (liek Xbox 360 or PS3), or you intend to watch HD films on Bluray - then the difference is FANTASTIC in my opinion and well worth the cash.