DB, yup, bike doesn't give any indication of time remaining. That would indeed have been a nice thing to have. I noticed however that they were bike stations near most major tourist locations, like monuments, close to metro stations etc. If a tourist doesn't mind the extra overhead of doing the bike switcheroo, he/she can get by without paying any extra fee, but I think it does spoil the whole sightseeing/exploration mood, so I decided to take that bite on my wallet, and simply enjoy. The innumerable traffic lights and the Paris traffic are the other irritants.
/Prashanth