My 25mm GP4000s are simply amazing. I put another 80 miles on them earlier today. They are mounted on Shimano DA 7900 c24 clinchers. I bought these tires mainly to see what all the hype was about (I wanted 25mm tires anyhow), and now I know why people make such a fuss over them. It's like they do it all. They roll fast and corner better than any tire I've ever used. I have much more confidence when I take corners now just because of these tires. Being 25mm wide, they provide a very smooth ride. Btw, I'm around 185lbs and run my tires at 105psi front and 115psi rear. The other really cool thing is that they seem to be pretty durable and tough for their weight. Mine are wearing very slowly, which is a nice bonus considering how nice and grippy they are.

Overall a great, high-quality product with amazing performance. I definitely found my favorite tire with these. Now I just need to pick up a 700x23c set so I have something a little more aero for my Reynolds carbon clinchers.