One of the owners of my lbs rides chorus 11 and he said he threw a wheel with a 10 speed cassette on and it shifted surprisingly well without any adjustment, just an extra click.

I personally would want 11... for no other reason then if I can afford it I want the newer stuff... I went with 9 speed 105 on my bike right as 10 speed 105 came out. I wish I had worked to get the new stuff.