[Klaus]

I'd want both as the best of both worlds

 

About degrading bokeh, what would be the mechanism? Are we talking about the design requirements or something to do with the shift itself?

 

Well, think about it. The IS stabilizes the focus point whereas the out-of-focus area suffers from a parallax effect:

http://www.bokehtests.com/page2/index.html

 

Think of a balancing a stick (=stabilized light ray) on your finger. The anchorage (=stabilized focus point) on your finger remains in place when moving the stick. Now think of the out-focus-area as one of the stick's ends.

This movement of the stick is equivalent to smearing in the out-of-focus area (e.g. a OOF highlight).

This is affecting mostly long tele lenses.