Since I do not have a dealer with in 90 minutes of me, I normally order my equipment through B&H or Midwest Photo Exchange, both offer great service.
I decided to purchase the Canon 300 2.8 IS lens and when I checked Amazon was $120.00 cheaper, and $3.99 next day shipping, had I went with BH next day would have been $50.00 more.
I believe I have ordered lenses from Amazon before, and they have came with the USA warranty, as long as it does, its a USA product not Grey Market correct. I am assuming Amazon would NOT sell grey market, if that is the case will return and buy from B&H.
Not sure if anyone else has ever purchased lenses, or cameras from Amazon before or not.