I have installed one in each of my airplanes - and did one for my -10, although I haven't used it yet (not quite yet done building...).
The issue posted earlier where the brake fluid leaked could occur if you set your parking brake in the cool morning and then it got hot in the afternoon as the brake system is a locked hydraulic system with the parking brake set (valve shut) and something's going to give as the fluid heats up. However, that would be take a significant temperature transition to make happen.
At my home airport, it's not uncommon to have winds 25G35 and the airplane will roll if you just get out prior to setting chocks. It effectively acts as a second person to hold the brakes while set chocks.
I find it invaluable for stopping on a ramp that has some angle to it, fuel stops or loading passengers where setting chocks to keep the aircraft from rolling is an avoided hassle.
However, I only use mine for short periods. Even so, it's a low cost feature I recommend installing during the build, that would be more difficult to retrofit later.