Up till recently I have been playing mostly with polyester strings - namely - Tecnifibre Red Code, Alu Power Rough, Wilson Enduro Tour and Kirschbaum Super Smash Spikey. Recently I decided to go for a change. Since I saw on the string logs of many tournaments that a very high number of pros use Lux / VS Gut hybrids I decided to try the same. I was expecting there to be only a slight difference as many people here have quoted that playing characteristics come roughly from 75% mains and 25% crosses. So naturally I was expecting the racket to play largely like a full poly job with a bit more feel and less harshness. Well, I am now using, Alu Power main (56) and VS Gut Crosses (58) and the difference from an full poly job is like night and day. Granted, I have only used this setup for the last 3 days but it really makes a huge difference for me. The spin seems just about as good (maybe marginally less) but power and overall feel have improved dramatically. I guess the deciding factor will be durability. So basically, while it is obviously difficult to quantify, I would say that the cross strings can make a far greater difference than 25%. Does anyone agree / disagree?? However, I can imagine that if I put a cheap syn. gut into the same hybrid it would have less of a positive effect.