[Deer Hunter]

Tigger
If you are thinking about secondhand be very careful especially with pro models - what have they been used for - how many hours have they done.
How do you get that special moment - with difficulty!!! research your subject fully - try and get local knowledge of your subjects whereabouts - be prepared to spend many hours, perhaps days waiting for that special moment.

Andy
Some will say there is a slight loss of quality when using a still lens - I have not found it. As I mentioned I use a Canon 100mm-400mm often, that over the years have produced footage good enough for the box!
Same can be said for the 100mm and 180mm macro I use both on both my cameras. Obviously you need a EF/Xl adaptor that's a costly item in itself. But I can't complain with quality.

As for using a Nikon lens on the Canon XL's this is new to me, but no doubt someone as produced an adaptor to make them fit.

I'm a Canon man through and through been using their equipment now for over 40 years both in still, cine and now video.