Yes they are quite light, much lighter unfolded than folded - the psychology being that when you try to pick up a small lump of metal you expect it to be lighter than a large lump of metal.
However, be warned, the ride characteristics are very different from a normal sized bike. You wobble more on small wheels and the bike is of course shorter. Practise on quiet roads. I only bought it because sodding Tramlink won't allow normal bikes on their trams, but it is nonetheless the key to green peaceful summer days along country lanes.