Well, I just installed my KORE leveling kit. I know it's not the whole enchilada, but I'll give my opinion anyhow.
I don't live near a desert, nor do I have any intent of burning up some dirt roads at 75mph. I do however have to drive on some pretty bad roads and highways.
My first impression was that the truck felt more unstable and a bit frisky on bad roads at slower speeds mostly. Other than that, I couldn't tell much difference beside the front end obviously being higher. After logging a few more miles, I am now really feeling the opposite. I think not changing the rear makes the difference that much more noticeable. I have hit some really bad places in the roads at higher speeds that I would normally avoid at any speed. The front end seems to absorb the bump whereas before a bad bump would resonate throughout the front end and affect the steering and sometimes alter the direction of the truck. Not now. You still feel the bump but it has much less affect on the truck. Like I said, I have the bottom of the KORE line and I can't imagine how much better the race system must be.
Sorry for the lame review, but thats real world.