I own them all on DVD and like them all in their own special ways. I really love Wyrd Sisters even though it is in cartoon format and when I read the book (which is one of my Pratchett favourites) I hear the witches’ voices as they are in the animated feature. The stand out feature of these for me was that they established Christopher Lee as the voice of Death. As a result, whilst The Hogfather had a wonderful look and feel, Ian Richardson just wasn't the voice of Death for me - that HAS to be Sir Christopher Lee. I really wish that they would go back and dub over Death's lines with Sir Christopher as that would make it just perfect!
I agree that David Jason did not make as good a Rincewind as he did Albert. Rincewind to me should be stringier, rangier and hungrier looking lol. I also felt Twoflower should have had an Eastern appearance - which becomes important when you finally get to visit him in his home country in 'Interesting Times' - which is very similar to China. Sean Astin did give a good performance though.
I liked Going Postal but agree that Charles Dance didn't look as much like Vetinari as I would have liked. He looked a little too 'safe' whilst Jeremy Irons got the edge of menace which Vetinari has just right - even though he cradled Wuffles all the way through his 'interview/audience' with Rincewind.
I would love for Sky to do more adaptations. The quality of casting, set and design is wonderful and the scripts are mostly spot-on. I think involvement from Sir Terry helps keep things on track more.
As long as there are Pratchett fans - and let's face it there always will be - they will find an appreciative audience.