I've bought several colors of B-55, and gotten a good bit of feedback on it so far. It's not in the same class as the HMPE materials, but it is am improvement over B-500--a little less stretch/creep, a tad better performance (same strand count). My cost is the same for either one.
I haven't invested in Dynaflight '10, because it would be a huge investment, and I'm not yet convinced there is a noticeable improvement, at least not with the majority of the strings I make. I've seen a lot of fads come and go, and I don't know yet if the tiny string craze is a fad or not. I know they only make up a tiny percentage of my orders, and creep doesn't seem to be a problem on moderate strand counts--at least it hasn't been for me.
There's not a huge difference in the price between '97 and '10, but when you are looking at buying 30-40 spools, it's a lot of money. I'm going to have to be convinced that it's worth the difference. That, and I've had less than a half-dozen customers even ask for '10.
Chad