recently replaced the chengshin/Kenda combo that came on my bike with a stock-sized set of Roadriders, roughed them up to the edge with sandpaper before mounting, and rode them slow for approx 50-60 miles... took them out this morning, did 100 pretty spirited miles; WOW!  I can feel a world of difference, both braking and cornering, it's almost unbelievable how stable they feel. Being new to the GS500 world, I may not have a large frame of reference to compare to other tires, but it would be hard to beat these bad boys. I paid less than 150.00 for the pair from Southwest Moto, received them in 3 days, great service. Many thanks to GSjack as well for his extensive knowledge. 

I also installed my roadriders about 4 days ago, and they're amazing. I had 14K miles on the stock bridgestones. Bad idea.

I bought a set as well... So far, MUCH better than my stock 12 Year old tires