I'm shopping for new tires, what are you riding on?
So far, it's the Spitfires that I am seriously considering.
For me, it wasn't really the specific brand(s), but just that the tires are new, and the ones I took off were very old. I think the rubber just got hard and was cracking, and I'm not sure what else was different. But I could immediately tell the new tires made for a much nicer ride.
Like I said, I don't think it's these specific brands, but since you asked, I have a Metzeler on the back and a Dunlop on the front. I didn't plan it that way; it's just what I ended up with. I ordered Avon Roadriders for my K2. I give the link to where I got them in my build thread.