I am spectacular in my inability to evaluate the potential of this currency.

Easy: none potential. The income is paid from inflation. We all know what happens when a country injects money in order to pay for whatever it wanted to pay.

However, I have signed up and I am receiving Manna once a week.

Yes. Good. That's free money, and having 1 satoshi more in your pocket is better and having 1 satoshi less. Of course.

A real economy should be created around Manna. If not, price will be going down, as most of the people will be selling their MANNA as soo as they can.

I have just also signed up. Sorry, as I did it before seeing your link. I would have used yours.