Why I am being down voted? I was just saying my opinion. Also this opinion comes from the fact that I have tried riding bike with my legs not on the pedals and it felt unstable and uncomfortable.

It is not unstable. It is uncomfortable because you are putting all your weight on your crotch, rather than on your (much stronger) legs.

That seems hard to believe. It is very nearly impossible to hold the bicycle for more than a few seconds when it is standing still, but I can ride it for half an hour (traffic permitting) with no problem.

but you can also ride it for as long as you like if you're going down hill, without pedalling.

That stability comes from the angular momentum in the wheels, not in the drive train.

The gyroscopic action of the wheels actually has very little effect on stability. It is the fact that the front wheel counter-steers when you get out of equilibrium that is the major reason for staying upright.

EDIT: Here's the link: http://www2.eng.cam.ac.uk/~hemh/gyrobike.htm

He says that the gyroscopic effect is small compared to the weight of the bike and rider.

The enhanced gyroscopic stability appears to be a near constant-rotating balanced mass; it's still rotating with the wheel but at an angular velocity such that the gyro effect is constant (ie reducing slightly as the wheel's own weight adds to the gyro effect?). Thus you get the gyro stability that you get when riding quickly with no hands but constantly, even when riding slowly.

It's neat for sure and bound to do well as it's hiding the stabiliser away and pretending the kid is more advanced, hence parents will love it as their kids will look "better" than the neighbours kid!

Thanks for that link, nice to see it worked out so well. I have a zephyr recumbent, which is very hard to ride with any amount of relaxation, I'm now wondering what the reason is that recumbents are as a rule designed with straight front forks.

I stand corrected. Thanks.