That is so true about every motor needing an encoder. The 3pi does do surprisingly well without encoders, but still would be much more awesome with encoders. The Zumo would also be much improved with the addition of encoders; I know that it is quite cramped around the motors, but would these possibly fit on a Zumo?
Wow, this looks like a great improvement over the old GP2Y0A02YK0F sensor! I really like that it has an enable pin, and 0.1" holes, so that wires or header pins can be soldered on, much better than the old ones with connectors. Not sure that I like that there is only one mounting hole now.
Does this one fix the noise issues on the power line that the old one had (I had to add extra capacitors to clean up the power)?
As part of the build team on Troubled Child I can say that the Pololu relay board worked great (once we discovered that the 12V relay board does not work at 5V, but the 5V version works great!). It was really nice that we could trigger the relays with a 3.3V signal.