The only down-side to using a 100% Dyneema material is you can experience some stretch/creep when the temps get high. Lots of variables that will determine how much--draw weight, string length, strand count, actual temps, etc. In some cases it may be none or so little you won't notice..in other cases, it can be a pain.
That's the reason blended materials were developed. Early on, the materials with total stability/zero stretch, like Kevlar and Vectran, were great for bow strings...until they broke with no warning.
This led to BCY (the founders of BCY also invented the original Fast Flight) developing the first blended material, which soon became known as 450 Premium. It was improved and became 450+, then another upgrade with 452X.
When SK90 Dyneema became available, it wasn't long until BCY-X was invented. There's no other material on the market like it--BCY has it patented, so unlike most other materials nobody else can (legally) copy it.