I'll update it and see if I can deploy it to the mainnet. I think it shows the potential of Lisk quite good.

This would be nice. At the moment there is no App on the mainnet (or I can't find it), which is really bad for a coin which was announced as "for JavaScript Developers". Will it possible to launch the App from the lisk.io online wallet then?
As simple as Guestbook Dapp it may seem, it's a good start for lisk and I'm hoping that more dapps will soon come to follow.