To be quite honest I agree with the fact the person is just enjoying themselves, and decided to post it, (The new version of showing your holiday snaps/films or hey look how my dog can push the ball) that’s what My Space and You Tube etc is all about, (The sound and video quality of the site playback systems is not good enough for demos) if you want to make a demo then do it on a site that is designed for it. (Or get it professionally done)
The Arranger keyboard is designed so that you can have fun playing at home, so just enjoy it.
If you’re a professional showing your work, then yes you are looking for constructive criticism, but then you wouldn’t be posting like a home player does.

Bill