This may only concern a narrow audience I imagine, but it just so happens that I narrowed my 'kit replacement' down today to the Sigma and Amazon had it back in stock.
(when I checked a few days ago, it was only available from a vendor at a higher price)
It's a good 'deal' too, in my opinion, compared to the usual places I do comparison shopping with:
Amazon: $395 shipped
B&H: $460 or so (depends on shipping)
Sigma4Less: $400 or so (depends on shipping)*
A few days ago when Amazon was out of stock I thought for sure Sigma4Less would be the way to go, but their shipping charge on this one is atrocious for some reason ($20 was their lowest rate-- ground, I think!?)
*AND remember that they only give you 1 year warranty on the lens as compared to the 4 years you get from Amazon or BH.
Check out this scan from lightrules in which Photography Monthly Magazine declared it the winner of the standard zoom shoot out.
Note that lightrules had the EX included in his own lens shoot out against the 17-55IS, 17-40L, and 17-85, and it did very well--- and that was the old version of the EX! The new one is reputed to be better in every way.
There, I did all the homework for you If you've been eyeing this one, it may be worth snatching it from Amazon before it goes out of stock again.