unless one needs the extra wide angle reach of a 10mm zoom, I'd say the tokina 12-24mm is an excellent choice for a wide angle zoom. At the other end, the Nikon 70-300mm is a really nice and reasonably priced zoom telephoto if you want that range as well.
Optically, I've found that Tokina glass is excellent and most folks could never tell the difference in images made between a Nikon or Tokina or Tamron. Having said that there's nothing like the build quality of a good Nikon pro level lens --- they are a joy to handle in part to their fast focusing and ergonomic design. A Nikon lens will also have a higher resale value, although I've yet to check this out as I can never part with any of mine!
I do a fair amount of Underwater photography and use my Tokina and Tamron glass in place of overly large Nikon lenses that are impractical in a housing.
For that purpose I use a Tokina 12-24 and a Tokina 10-17 (fisheye) for wide angle work, plus a Tamron 90mm macro. They are all excellent.