I have traveled on the Canal du Midi on two occasions. Some thoughts. The top speed on the canal is 8 km/hr, or just shy of 5 mph. At that rate of speed, assuming no locks, the longest distance you can travel is about forty miles in an eight hour day. Unfortunately, however, there are locks about every two miles or so. Each lock takes from 30 min to 1 hour to traverse, assuming that your boat is in the first group to arrive at the lock and can enter the lock without waiting behind other boaters. In terms of speedy travel, the canal just ain't the way.
We saw some barges which were not self guided, but in our experience these were live aboard journeys rather than sightseeing opportunities. I would be surprised to find a short haul tourism service on the canal. There is, however, a trail which runs along the length of the canal. This trail is a remnant of when the canals were drawn by horses. Usually the trail is covered with gravel, although it may be dirt or mud. If you rent some bikes, it may be fun to travel that way on the trail.
Traveling the canal is a restful, leisurely event, and while you don't travel very fast or very far, it can be a great way to spend a week. I don't think it is conducive to much sightseeing, however.
