Have used this on several occasions, both the Left and Right hand variety - easy and intuitive to use, can be used with relative ease in cramped surroundings and has little to no slippage when weight is placed on it. Would not advise to use this in a situation where a sudden load would be placed on it if possible (such as when arresting a fall) as it will damage the rope, possibly quite severely.
It is a heavy piece of kit to carry when climbing, and there are better alternatives to carry with you on a rack (or just some Prusik cord!). I would also recommend that a karabiner is used on the uppermost hole to ensure that the rope will not "fall out" should the cam be pulled back accidentally.