Conclusion: This lens is very well built, it may not be fully sealed but in my opinion that's the only thing stopping this having a red ring. The lens does not move either the front or rear element for focussing which means it is naturally reluctant to attract moisture or dust internally. The proper ring-USM focuses nearly immediately, it's frighteningly sharp even wide open, the Boke and low light ability is lovely thanks to its wide aperture. What would I change?
Pros: Fast auto-focus, Superior build quality, Super-sharp images, wide aperture