As a musician it's extremely handy to have a portable keyboard around with which you can quickly tune instruments, or pick out a melody that comes to mind. That's the main reason why I bought this, but it does so much more!
The production of sound is pretty consistent, and the unit goes surprisingly loud out of its own speakers! There is a minor 'blip' when transitioning between notes that you don't really notice through the speakers, but you DO notice when playing through the (nevertheless handy) line-out socket. The functionality of plugging in mp3 to play along with is another great touch, and doubles up the unit as a bedside speaker.
There are three preset sounds of varying tone and pitch, plus a tuning wheel on the back of the unit that lets you tune the keyboard continuously to any pitch you like within a large range. Turning this when playing, you can produce groovy slides and glissandos! By far my favorite element is the vibrato function, that produces a lovely flowing vibrato similar to the sound of a hammond rotary organ. With this you can replicate riffs like 'kids' by MGMT to almost perfection.
I've made it clear that I enjoy using this instrument 'seriously' - while its undoubtedly great fun and would make a fantastic toy for any child, I intend to record with it and use it live. Its a bit quirky and a bit different but the range of sounds and tunes you can get out of it is very impressive.