Very commonly used by the AE86/rolla guys. My BCs give me -1.2° camber which for my tyres is plenty. I had a digital inclinometer that I used to set the camber on a flat surface but that got stolen along with all of my other stuff. Provided you torque them up correctly and use some threadlocker there's nothing wrong with using these at all. Toyota actually make their own 'crash bolts' that are very decent from what I've heard.
You can also use the angle sensor in a smartphone to get a rough measurement with the right app. Tested back to back with my inclinometer my Galaxy S2 was accurate to within .1° but an iPhone 4 was within .05°.
But remember, the more negative camber you set the less rubber you have on the road for straight line braking. I'm going to get some camber/crash bolts at some point to even up the negative rear camber on mine, I think I had 0.7°/0.5° L/R.