Nike + iPod Sport Kit

Pros: Great motivator for running and a nice training tool. Helpful for planning out runs based on distance or time. When it works, it's a great product. I've found the accuracy (when calibrated) to be good. Can buy pouches for use with any shoe.

Cons: I had to return my first sensor because the unit wouldn't recognize it. The second sensor also has issues. I have to go through an elaborate turn on/turn off/turn on/ repeatedly tap the shoe sensor to make it work. Unreliable product

Summary: If you're willing to be patient and work out all the glitches, it's a great product. It can also be a huge pain due to the bugs inherent in the sensor recognition. The Apple web site has lots of tips from users that are useful to solving these, which helps. If the bugs were worked out, I'd give it an A+. As is, I give it a C.