I bought some Shimano R540's this afternoon. I had talked to a salesman at the LBS about buying these and he wanted me to bring my bike in so that he could install them and put me on the trainer and adjust things. This also allowed me some practice clipping and unclipping as well. I did a short ten mile ride tonight without incident. One thing that had to be adjusted was seat height. I think we raised it about an inch. My leg was very bent at the bottom of the down stroke which I guess is due to the difference in thickness of the cleat and shoe? Any way, I could tell a huge difference in efficiency especially when climbing the very small hill in my neighborhood. I still need to do some fine tuning with cleat position, but I'm sold!