I have my original Diana 27 from 1968 or thereabouts. My Dad bought it for me at the post exchange at SHAPE, Belgium. I started shooting 10 meters indoors at tiny little paper targets. Got fairly good. Moved to South Carolina for a year while Dad was in Vietnam, where I took up hunting and plinking in the woods. That one year was formative to say the least.
I have the Diana apart right now, new piston, spring and seal. One day I'll get it back together.
In the meantime, around 2012, I got back into the airgun world, and bought my second airgun. It is an RWS / Diana 350 Magnum .22 Compact Pro.
That thing is difficult to cock, and difficult to shoot, and it is a violent airgun. If you can learn to shoot that thing you can learn to shoot any airgun.
I've killed the original RWS Scope that came with that gun. I think they are known to fail. But there is still something compelling about a powerful springer. Not for a kid though. My 11 year old can not cock the beast, and I struggle.
At any rate, the Diana 240 is a great choice. I kinda want one.