You may want to add the CS-041 to your list. It is comparable to the 256 in weight with improved stiffness.
I think the 256 does have more issues than the 056/057, but that said, there are plenty of them out there without any issue. My 256 is a year old and has 1000's of miles on it. Perhaps it is more due to rider weight?
What type of geometry do you prefer? How do bikes you've had int he past compare to these frames? That is how I ultimately chose my frame size and all.