This can both be viewed as a toy, perfect for killing some time in the bus (with headphones) or as an instrument for a live setting.
It is essentially an effect, and i have used it primarily as an effect for samples or other synths. It sounds great, and the simple features are basically all you need.
On the downside, the 'keyboard' is pretty much impossible to play, as it covers 4-5 octaves. If it had been the same as the monotron duo, this had been much more useful. Also, make sure to always have extra batteries, because it eats them up pretty quickly (and doesn't take a power supply).