Thanks for the review Bill!
B-55 is BCY's "new" dacron string material. It's not meant to replace FF type materials.
It seems to have a lower amount of stretch/creep than BCY's B-500, but it still has a lot compared to Dynaflight '97 or 8125. I have a jig that I use to put my strings under 200-300 lbs of tension--they draw back up some, and how much stretch you get on a bow will depend on a lot of different factors: strand count, draw weight, temperature, etc.
Still waiting to hear from several others, both long and short term opinions. I don't think B-55 will be a "magic" string material (no such thing IMO), but so far it looks like it will be an improvement over B-500.
Chad