The first thing that struck me at the time of opening the package was how solid it felt. For a toy with such a low price it was of surprisingly high quality. The shape is that of a keytar (keyboard with a guitar grip), so you can just as easily hang it around your neck as you can place it on a table.
The song support for this product is unfortunately quite limited, but to make up for that you are able to play guitar or bass as well.
As accustomed to a keyboard as I am, the basic mode is a bit too easy for my taste, but there's where the pro mode comes in. With the pro mode you can actually learn to play the parts as on a real keyboard, though the somewhat limited range (just over 2 octaves) has forced the developers to do some workarounds. Still, if you take what you have learned from Rock Band to a real keyboard/piano, you should be able to figure it out.
On top of that, the keyboard is fully MIDI compatible, meaning you can plug it into a MIDI sequencer or a PC (using a regular MIDI cable - sold separately) and actually make some real music.