Well I was impressed with it.
I wasnt sure about Death when I saw the trailers , just didnt look right, but he was only in the red outfit. Last night you saw him in his cowl and I felt it was a very good representation and made me realise the wrongness I felt seeing him as the hogfather was probably the desired effect.
As for the voice well other than maybe throwing some special effects of somekind on it the best you can do is to get a classic actor with a distinguished deep voice to do it...and Ian Mkelland fits the bill as well as anyone.

Didnt see enough of the wizards so I cant comment on them.
Teatime was a really good choice. I didnt recognise the actors name but once I saw him I recognised him from a few things including an episode of Dr Who (the one thats about the origin of plastic surgery women...cant remember her name or name of the episode...I know Im crap)
Anyway, soon as I recognised him I wasnt sure as he normally plays cockney wide boy type of roles...but from the clips I saw he was suitably creepy/dangerous/enigmatic.
David Jason...nuff said.
Nigel Planar looked right in the role of Mr Sydney.
The little bit of Deep Thought I saw looked good.

All in all Im looking even more forward to seeing the film!