Has 20+ years of SLR/camera experience.
Incredibly sharp; very solidly built.
It's heavy, but who cares?
I totally adore this lens. I finally put it to good use on safari in 2009 (having bought it nearly 2 years earlier). In combination with an F1N and a suitably bright, centre-weighted focussing screen, it was an absolute joy: focussing smooth and positive; lens well-balanced. Even in fairly low light (an hour after dawn, say), focussing is no problem, and it is capable of pin-sharp performance: I have so far enlarged up to 15x10, and the best shots are still very sharp indeed.
It is very well built.
You have to watch the weight, though: a monopod helped, but proper stability came only with a tripod or a rolled-up sweatshirt. Hand-holding not a realistic option except for strong arms taking motion shots (and even then a bit hit-and-miss).