I've had them on several bikes. The first picture is a Trek 930 and the second one is a Rockhopper. One important thing is to resist the temptation to put grips on them (as in a picture posted above). That puts the brake levers WAY too far inward, all the way to the inside. Try to ride with your hands that close together, and you'll feel very unstable - just the opposite of what you want under braking. Move the levers as far to the outside as you can, and still leave room for your hands. Even then, I never felt like my hands were quite far enough apart if I needed access to the brakes.
After the novelty wore off, I switched back to drop bars after a few years. Keep in mind also that if you're coming from flat bars, this brings the main handlebar position (the bottom part) a lot closer. You may need to change stems.
