This is my first foray into full frame lenses so cannot compare with other lens makers but so far very happy with this product.
It's crisp, autofocus is fast and also quiet.
The lens seems built well, with the heavy metal tripod mount a bonus, as it's quite a chunk compared to cropped frame DX lenses!
Overall very pleased.
Staff were also helpful as when I ordered it it was clearly marked out of stock. When I called they gave me an exact delivery date and it was fulfilled. :)