I got a chance to try out the full X1-Biphase 17 a little sooner than expected.
First impressions were very good. I can definitely feel a difference between the full bed and a hybrid setup. One thing I've been noticing is the consistency in how a string feels when you put it on a racquet, and how it feeds back into your arm when you play.
I had a heck of a time putting full X1-Biphase on because it's so stretchy. However, that is the best trait of multifilament. It had more "power" than say... Prince Synthetic Gut Duraflex. I think this is do to the more "stretchy" nature of the string. It definitely plays a lot softer and more comfortable too.
I guess you can compare hybrid and full bed to racquet stiffnesses. The hybrid setup made my racquet feel like it had a higher stiffness rating. My serves were moving a lot faster but my groundies didn't have as much control. The full bed of X1 felt like my racquet had a lower stiffness rating and my groundies were more controlled but with less power. I did mention that X1 Biphase had more power than PSGD and even though PSGD is stiffer, I still hold to this.
As a closing note, X1-Biphase moves a lot, even after 1 hour of play. I don't know if this is normal for multifilament or if I did a bad job of stringing the mains. I did have a hard time getting the mains to tension consistently because this stuff stretches so darn much. I'll have to try to be more consistent next time to compare. I'm definitely going to stick with this string for a couple months.
Babolat Pure Storm Ltd. (X1 Biphase 18 @ 53lbs)