It took a while with the holidays and finally some snow for skiing to find the time to install the sensors. I ended up installing the on/off switch on the front driver panel, just under the four buttons below the mirror adjust.
Installation took me 12 hours from start to end with dinner break, video recording, figuring out the wiring to the front, wrapping the wiring with a tubing, finding the tubing, deciding to wrap the wires with tubing, etc. Yeah, I took my time with this. I bet a casual installation according to the instructions doesn't take more than 6 hours.
The crappy video, due to low light is on youtube:
It's amazing how little screws are used. Everything is just snapped together plastic. The hardest part was the removal of the side panel since the folded seat still pushes against it and prevents easy removal. Follow the instructions, especially when drilling holes (i.e. the outer sensors are 24mm while the inner sensors are 26mm; also the tab of the left outer sensor is on the top so you'll drill the big hole in the bottom pilot hole while the top one is used for all the other ones).
It'll take some time before I can comment on it's usage and usefulness since I just installed it and don't drive much on regular basis (i.e. I try to commute with my bicycle and keep my fuel consumption lower than some Prius owners

). But I can already report that whenever you put your car into reverse it does a beep to assure you the backup sensing system is on, something that my 2003 Explorer Eddie Bauer didn't do.
If you have any questions ask while it's still fresh in my mind.
BTW, if you order the backup sensing be aware that there are two parts to purchase, the sensor and everything else. Some dealers sell both as a kit. So just double check when ordering.