[Andrew Schreiber]

I should have been more clear, I dont like them for sensing position of a system that has slip. My issue with them was that our drive system had this knack for accelerating quickly and the wheels slipped occasionally. This meant that our robot thought it was further than it was.That being said, I would use these if I needed to know how fast a gear was spinning due to them being a no contact sensor. Mounting an encoder would mean that the encoder shaft would be spinning at High RPM which causes wear and the potential to have them wear out. In short, it depends on your use.