[magnets]

To address the open/closed loop control issue-
The confusion probably comes from the fact that the poster isn't too familiar with implementations of closed loop control in FRC. It's really hard to make blanket statements about one method being faster than another, or one being more reliable than another unless you have spend a significant amount of time working with both.
I do agree that a well-written closed loop control (PID, bang-bang, take-back-half...) is much superior to an open loop version, but in some cases, a team with little programming resources may not need to have PID control on their arm, but instead have two end of travel limits.
My recommendation to the poster is to spend time in the offseason experimenting with different control methods before commenting on their effectiveness.

As for the optical sensors, our team uses the banner IR sensors. We've used them on our drive wheels, our shooter wheels, and to detect the bump in 2012. We've found that with high speed control, we'd sometimes see that the speed reported would get cut in half when we went to competition, due to false positives. We fixed this by making sure that when we did high speed sensing, the black and white parts of the shaft that the sensor looked at were equal lengths. This makes it harder for the sensor to skip over one of them and report the incorrect speed. We also turned down the sensitivity as far as it would go without loosing the signal.