I just bought a Korg MicroArranger and really love it. I've discovered that you can do techniques on the micro keyboard that you simply can't do on a regular keyboard. Because I play accordion, the keybed feels so comfortable and the sound is tremendous; not to mention the excellent selection of styles to play off of.
The MicroArranger is a real conversation piece when I take it to "jam" sessions. I get a big kick out watching the Jazz snobs face's when I blaze thru Chick Corea's "Spain" including left hand bass. Also, I don't have the problem of having other pianists trying to dominate the jam session; the micro keyboard stops them in their tracks.
Take a look at what Jordan Rudess does with the Korg MicroPiano. http://korg.com/Mediaplayer.aspx?md=4888&ar=307
For the price, it's the best keyboard investment I've ever made. I highly recommend the Korg MicroArranger.