loads of people do it!!! it works quite well, the brake returns quicker with water than with standard mineral oil. The main problem is that it can cause the piston in the leaver to swell, and can also cause leaks. If you have a warrenty, I wouldn't recomend doing it as it will void it instantly. Also with it being, quite chilly this time of year you would be best of running a water/anti-freeze mix to stop the water freezing in your brake, cracking the hoses and generally fudging the brake.