Sorry if you don't believe me - I don't have pictures or video underwater but see below - but the first one I bought was one of the GTI copies (200 watt motor and metal gearbox) and it pulled me and my buddy, both in twin sets. Admittedly it was only at a leisurely pace but it did do it for 40 minutes. I always dive a twin set and have used both the twin speed and the single speed with it and they can pull me at faster than a normal relaxed fining pace (which is normally quite slow). Having used my first unit 2 up I have two friends who bought the same unit and I bought 2 more. I then bought 2 of the single speed units. There are NOT Teknas or Gavins or even Torpedos and I'm not recommending them for people who want a serious scooter - nobody should expect to get a serious scooter for less than 100 bucks, but they do work and for messing about they are good fun. It's all about expectations, I assumed for the money they would be crap but was surprised, if you expect a Gavin then you will be very disappointed.
I have a picture of an AOW course - that's me on the right in twin 12 litres, with suit inflation (not exactly that streamlined) - that guy on the left is also in twin 12s and the middle diver is in a single 12. We did 3 circuits of the lake behind us. Mine is the twin speed version and the other two are single speed versions. Nobody felt they were too slow and we certainly covered about double the distance we could have done without them.
http://www.cambridgediveandwatersports.co.uk/training/courseimages/aow-04-07a.jpg
The original post said they were all crap and not worth buying, all I'm saying is what my experiences with them are - I've no reason to lie about it. One last comment, a 200 watt motor is probably more power than the average person can generate for very long without getting very tired underwater, you certainly won't do it for more than a few minutes - 750 watt is one horse power I believe.
Paul.