As i mentioned in my last post. I have used a 400/4 DO for a long time.
I really liked that lens.
The upgrade to a 400/2,8L IS USM was forced, overall it´s a good thing.
Optically the "new" (i.e. used) lens are a lot better. And i just love the possibility to use a really short DOF (depth of field) to create really clean backgrounds.
Aside of that, i just read a great quote:
"You are never to old to set another goal or to dream a new dream"