This tour was cool, especially if you don't have a lot of time and want to see the big sights. I am NOT normally a tour bus kind of girl, but I liked this option because there are four different routes that all connect, and you can hop on or off any of the buses on any of the routes. I was able to see many big sights in a short amount of time and take some great photos by sitting up top in the open-air portion of the buses.
The downside - the automatic audio guided tour kept cutting out (on every bus I got on), so you couldn't always hear the commentary, which was annoying. The upside, no confusing subway. If I was going to be in Paris for longer than a few days, I would definitely take the subway.
This a good option to maximize your time and sightseeing.