Oops sorry Marc i forgot to answer your question .
Well the lens is great if handled well

, not as i did mostly with too slow SS

.
The IQ is stunning for that " old" piece of glass , but when it comes to handling ............ way too big and heavy , i would prefer the new 600 MK II as it is way lighter and even hand holdable .
But at that time ( 2010) i would have bought one if had the chance to get a good used one . Other problem would be how to travel with this long thing ......... ??? specially going overseas ???
But there are rumors that Mr Canon is making a lighter version II , maybe a DO version like the F4 / 400 DO IS , but for now i am more than happy with my two big glasses ( 200-400 and 500 MK II )
If i would get the chance again , to get it for a week for a special project , i would take it with me , for sure. But only when i can go with my car .
Hope this helps , Marc
Cheers andreas