ScotchCal is a clear adhesive film that is applied to the paint in sheets. It comes in rolls with a backing that peels off prior to installation. It is perfectly clear and will not fade (I've seen some about 5 years old that was still crystal clear). It needs care just like the clearcoat on your paint. Don't scrub it too hard and wax it regularly. If the vehicle is well cared for (cleaned and waxed), the ScotchCal stays as nice looking as the paint. It could leave bubbles if it wasn't applied right. It is pretty easy to work with (judging as a spectator), and there's no reason to have bubbles. The installer will use a tiny syringe to poke holes in the problem bubbles and release the air if they can't lift the film or work the bubble to the edge. I still wouldn't recommend this as a do-it-yourself job, though. Have someone experienced do it.
As for being removable, that's something I don't know for sure. If applied on good quality paint, you could probably remove it without problems. The paint would have to be cleaned and waxed afterwards, but it should hold up. It is a good adhesive though, so I could see it pulling up some paint if there were any chips or loose paint to start with. Generally however, ScotchCal is a 'apply it and leave it' product. There is really no reason to remove it.
Rob