I have tried the Newtons. They were a good transition shoe into midfoot/forefoot striking. After I got the form down though (after about a year and a half), I found that I didn't need them anymore...and I could live without the price as well.
I then switched to Nike Lunaracers. They were great shoes. Probably my favorite shoes ever. Very light, real flexible, yet responsive. However, after about 250-300 miles, they started wearing out real quickly. Also, not many stores carry them anymore, as I believe they were discontinued.
Just purchased the Kinvara 2's and Nike Frees. The Kinvaras are very nice shoes, but I still feel like there's too much of a heel on them. The heel-toe drop must be larger than the Lunaracers and the Newtons (virtually no heel-toe drop on those.) I prefer the Frees, but I'm giving them both a shot.