Not endorsing it, or dissing it, but here is some research posted on the "Beet It" website http://www.beet-it.com/research/ (there may be some selection bias here - they probably wouldn't post any negative findings, but these may, of course, not exist).
I'm drinking it daily now - interested in the endurance and blood-pressure effects. I dilute it with apple-juice (about 50:50) which makes it a bit more palatable. I also tried the Beet It concentrated shots pre-Brighton marathon. These were quite tasty really - earthy, but quite sweet - a bit like undiluted Ribena!) As with other posters, I can't discern a particular effect (no single person ever could).
As regards the pink wee: the main problem with this is that you can't use the colour of your wee to assess whether you are dehydrated.