I took a chance on some Nitto NeoGens and I have to admit I'm impressed. I waited until today to do a review since we finally got some rain.
My previous tires were Kumho 712s.
Pros:
The Nittos seem like a better deal. They have better grip when cornering, quieter, better riding, and are cheaper. They don't squeal. Wet traction seems about the same as the Kumhos. Keep in mind I am comparing brand new NeoGens to some pretty worn Kumhos. I still think the Nittos are better in these categories.
Cons:
I haven't tested threshold braking with them, although my gut feeling is that it won't be as good due to the tread design (less aggressive tread and M+S compound on the inside of the tire + negative camber = compromise in braking?). Also, turn in seems a little worse although my steering rack bushings are so mushy it's hard to tell exactly what is happening. I'm also running less pressure than the Kumhos right now.
I like the theory behind the NeoGen's design. They are intended for cars with negative camber. They have the harder compound and all season tread on the inside. They have much more aggressive tread on the outside. This supposedly keeps the tire wear more even (assuming negative camber) as well as giving you a "best of both worlds" tire - aggressive tire when turning, docile tire when driving straight.