Deep breaths c&c, it's just an adaptation, it won't take away from the magic of the books.

Now, they aren't going to get Death's voice right until they develop the technology that dumps words directly into your brain without needing to use all those unreliable air molecules to transfer the sound. I haven't actually seen the trailers, so I don't know whether it is bad or not, but the important thing for the actor is to convey Death's emotions properly, not the accent he delivers it in. It would have to be a really bad accent (I dunno, a high pitched Mexican voice maybe - though that would be freaking hilarious), to spoil the show as a whole.

So to conclude, my advice is to watch the programme first, then make your decision as to whether it was worth watching or not.