I rent my eBikes at Rent a Bike. You can reserve them online a few days in advance. The confirmation is not automatic and may arrive one or 2 days later. They have also idea's for tours, but the easiest is to select and order a Guided Tour on our site.
You find them on -1 floor, under the main entrance hall. Take the escalators down, then in front of the Mac Clean go left. After 50m you'll see the counter.
If there is nobody, hit the bell till you hear someone answering.
It's 50 CHF for a day to rent. (Aug 2011) Be sure to bring a valid ID card or driver's license, which they will copy as a kind of guarantee.
You'll get a brief explanation how "it" works. But to save on time you can also read it on this website and be prepared already. Then with the bike in your hand you'll understand more easily. But be sure to try all functions there before you actually leave.
You get a 2nd battery if you ask for. so you can do like 160 kms with electroassistance.
Actually, the -1 floor is a huge and protected garage for bikes. Costs 1 CHF for a day to put it there. It has two exits that you can use to leave the parking and get into the town. In front of the counter of rent a Bike, go left and follow the corridor. When it splits, you can ge left and you'll get on the large square in front of the Bahnhof, where all trams and busses are. But if to take the right corridor, you'll have a long way before you get out, and then you are on the other side of the square. So you did not have to cross the dangerous road.