My Micro arrived last Friday. Out of the box it was ready to go and sounded great. As all the owners have already said, this is NO TOY. It is actually a PA50/60 in a smaller skin. The build is great, very sturdy. Most people ask about the keys; yes they are slimmer and shorter, but no slimmer than an accordion key with a much better keyfeel.
The thought of playing a mini keyboard may turn some people off. I find it exciting and fun. As I said in another post, the keyfeel encourages you to play to the strengths of the board. You can and will adjust to the smaller keyboard if you want to. If you choose to use the Micro as just a sound module, you'll have one dynamite of a sound engine.
The last Korg I owned was a X50, the last arranger was an iX300. Neither of these two boards were as sonically pleasing as the Micro. The sounds may be a good 10 yrs old, but they are good and lively. The Grand Piano, ep's and organs are my got to sounds - these are all stellar. In all, I must say that the soundset and drumkits as as good as - and some better than - my Yamaha s910. The styles have more of a live feel than the compressed, canned Yamaha stuff. Playing a style entices me to play - anything, even creating new songs and sounds.
I could go on and on, but the bottom line is that the MicroArranger is a solid, credible sound source AND keyboard. It is as good as any arranger I've owwned except the G70 - that includes my present s910. I missed not being able to take it out on a job today because I hadn't yet learned all the nuances of the OS that I needed to play seamlessly. Tonight, on the Twelfth Night, I had my Epiphany and now I think the Micro will go with me to the next job.
It has a mini 1/8inch stereo jack for audio input. I haven't decided whether I will attempt to run my mic thru it or thru a Harmony M and then thru the L1 Compact. Everything else on the I/O side is regular size and runs under the regulr Korg OS. If you've never played a Korg arranger, it may take you some time to undertand terms and the screen and buttons layout. Once you understand how styles, song play, performances and STS's work, you'll probably want to play this mini arranger all the time.