Zombie!Vimes is perfect. And so are his last words. And you've got all the characters' voices spot on, and... *squee* (I really need to get me a Discworld icon.)

I do have one nitpick, though: Nobby's younger than Vimes. I can totally see him as a decrepit old man, but he'd only be, like, fifty- or sixtyish at this point on the timeline, judging by him being a street urchin at the time of Night Watch; I didn't think decrepitude generally set in before around eighty or so, although you never really know with Nobby.