I purchased a pair of the Shimano Tri shoes from Performance Bike for use with X-2 Speedplay pedals(which I already had). When I looked thru the Speedplay documentation prior to attaching the cleats, I found that they are not recommended for use with carbon soled Shimano shoes. I called Speedplay direct and they said that due to the width of the carbon soled shoes, the X-2 is not acceptable with the Shimano tri shoe. Only the Zero is an acceptable cleat/pedal.
Luckily, I had not opened the packaging for my new pair of X-2 pedals so I was able to exchange/pay the difference for Zero pedals. I have attached the Zero cleats to the Shimano shoes but have not yet had a chance to take them out for a ride. The shoes do feel very comfortable.
The Shimano shoes and the Speedplay Zero pedals have gotten really good reviews. One place to look at reviews of both products is at
www.bikesportmichigan.com Hope that this helps!
David