There are plenty of good use cases where mini keyboards are worth getting. Portability and control are among the main ones. If you are an Ableton user looking for basic control and the simple input for bass lines, drum pads, chords and simple melodies then they fit the bill for short money. As a keyboard however they are just ok.
I have the Akai Mini but also just got the new Nektar GXP61 as my main keyboard. Not a lot of control features but a better full size keyboard with features like aftertouch and only $229.