I don't have anything to compare to as my first and only set of clipless pedals on my road bike are SPD M520's. Like blcknspo0ln, I also like how fast and easy they are to get in and out of and I also don't have to look before clipping in. I am clipped in with both feet before any of my teammates are with their road pedals and I don't have to clip one foot in when I push off. I've been riding on them for a year (and 3,000 miles) and haven't had any problems with them. I have ridden with friends that have Speedplay pedals and have had problems unclipping if they accidentally stepped in sand and didn't clean the cleats before clipping in. It doesn't happen all the time, but often enough that I won't use them. I also ride with a buddy that uses Eggbeaters and they are very fast and easy to get in and out of.

However, since you already have the road shoes, if your shoes don't accept the two bolt SPD cleats, then you are pretty much destined to choose from the pedals that accept the cleat pattern of your shoes. Good luck with your search and hope you find the right set of pedals and cleats that you are comfortable with.