Several months ago, I had purchased the Nikon DX 55-300mm AF-S VR lens for use on my Nikon 1 setup with an FT-1, and frankly, I was not overwhelmed by it, especially when shooting at the long end, wide open. As a result - along with the general unavailability of the 70-300mm Nikon cx lens, as well as it's quite high price, I decided to take a shot on the Tamron, after seeing another post that, at least with current firmware for the bodies and the FT-1, the lens works. Particularly as I was able to score a for all intents unused example of this lens with papers and box, on ebay for $233.50 including shipping. While I am still in the process of a rigorous evaluation, and I do not have the either the Nikon 70-300 cx lens, nor the Nikon full frame 70-300mm AF-S lens to compare it to, the short answer is, the Tamron is a noticeable step up from the Nikon 55-300mm AF-S DX VR-G lens. Specifically, what I've concluded in my first day of owning this Tamron lens: - The Tamron is significantly sharper wide open at 300mm than the Nikon DX lens is - really, the Nikon needs to be stopped down a stop at 300mm for any sort of quality, whereas the Tamron is fully usable wide open. - The VC (Tamron's name for their Image Stabilization) is better than the VR implementation on the Nikon DX lens, which is noticeably twitchy in the viewfinder. - The Tamron lens is better constructed than the Nikon DX lens - and it's lens hood is significantly better as well - The Tamron AF is at least as fast and accurate as the Nikon DX lens, and you can manually focus it while it's also in AF mode, something the Nikon can't do. - The Tamron lens seems to have much nicer bokeh than the Nikon DX lens, which in some ways resembles a mirror lens on out-of-focus highlights. - The Tamron is also a full frame lens, if you need it to be: On the downside: The Tamron is noticeably bigger, heavier and bulkier than the Nikon DX lens The Nikon DX lens is typically available used for around $50 cheaper than the Tamron is The Tamron works fine with the current body and FT-1 firmware releases, but who knows about the future. As a result, my Nikon 55-300mm DX lens is on it's way to ebay.