I have an Akai Professional MPK Mini MKII (has 25 keys), at first I thought it was cool, but then ran into trouble (I was using it to learn piano). It only has 2 octaves at a time (have to push a button to go higher or lower), so I couldn't even play Jingle Bells on it. I think if you are the type to slowly input notes and not play in real time or aren't going to need many octaves at once, it's fine, but I found it to quickly become impractical.