Wow! This Ableton Live kit on the demo video looks nice.
http://www.ableton.com/live
Recording sounds and tones in different mode and changing and rearranging it until it sounds good would suit me since I don´t play piano or guitar but I know what I want when I hear it.
I can imagine it´s even better if the final mix, layer by layer, can be played on real instruments of course. Ting-a-linnng!
However, I have a feeling I would have to find controllers and gears with more and more buttons to get THAT particular sound. I guess if I had time and money enough I would end up as JMJarre. I´m talking about the amount of gear of course