Feature:
It does the job. I like the sounds generated by this engine. The way it integrates with the rest of the M3 is impressive as well. I like the idea of combining two different synth approaches in one workstation. You can also use Karma to add more flexibility of control to the organic sounds generated by the board. Finally you have the vocoder which is an improvement to the one that comes with the M3. It gives you the oportunity to record phrases to be played later, like the Radias or the R3. The only reason I give a 9 to it is that I would like to have more sounds. You can program them an save them on the M3´s banks.

Quality:
It´s a board. Unless it comes defective (which I really doubt) you won´t have problems with it.

Value:
I saw that this is often compared with some other virtual analog synths like the access virus or the prophet. I agree that the last are more advanced, but we have to understand that they are in a different price range. I´m very pleased from what I´ve got. It gives you more sound creation and song composition posibilities.

Desirability:
Well, I can´t say I felt in love because of what I saw. Again, it is a board. You have to hear it to convince yourself that you want it. Go to youtube and hear some of the Radias demos. The sounds are different but you will get an idea of what the sound engine is able to do. There are some EXB-Radias demos as well.

Sound:
The sound engine that comes with this board adds more organic sounds to the M3 inventory. This board uses Virtual analog synth models which gives the possibility to create (and control) sounds that would be difficult or impossible to create with kind of synthesis. The only think I would like is to have more sounds (it came with only 128, half of the amount that comes with the Korg Radias). You can download some Combis from the Korg site that are very nice and useful as well.

Ease of Use:
The user interface merges smoothly with the M3´s OS. It is as easy as using the M3, with all the facilities that the touch screen and the intuitive OS gives to you. Also you can use the other controllers (joystick, faders, pads, ribbon controller, etc) to tweak your sounds.

Support:
I´d never use it.

Overall:
From the 3 options that comes for the M3, I think this is the first one you should buy. I love most of the sounds of the M3, and having this board gives me more tools to express myself using this instrument. It is an affordable option for a virtual analog synth and it works perfectly with the M3.