We have never used the ones linked in the OP, but I did mount a couple for a preseason project and didn't like them at all. Too many things to go wrong. I like these:
http://www.usdigital.com/products/en...otary/shaft/S4
We get the ball bearing version and have never had a failure. Some have been around for a number of years. I don't like the tiny wires and connectors, those do fail and need to be replaced. They're easy to mount and we just hook to the shaft with snug fitting surgical tubing. They are pricey, but as mentioned above, I get that back in time not messing with them and we use them over and over.
We will also test the ones we got with FIRSTChoice. I prefer encoders with a shaft, but the price is better and they look like a good compromise.
Ivan