Bert,
I've got the old 160mm f3.3 and it is superb, this new scope is meant to be even better. FYI, here is a centre + corner crops from my 160 f3.3 on a 300D:
http://www.pbase.com/terrylovejoy/image/33613032
Keep in mind with the obstruction the effective f Ratio is closer to f3.5, not that it matters that much
Terry