My own computer experiences date back to the development of the IBM System/360 (on a "Usability Team", what today is called the UI) and I've (painfully) kept up with the technology.

Each of us have our own needs. I'm not a master of my ES. I need to coordinate interfaces, experiment with different samples, play with different effects to see just what they are/do, Sometimes I need to do them at the same time (hence Windows). (I can recite the 6800 instruction set in my sleep, so this isn't a "Smack Mac" comment. My needs include more open architecture than Mac offers, that's all.)

I'm primarily a woodwind player, so the MO keyboard is already a compromise. I don't like the fixed vibrato in the woodwinds, and need to modify it. As the above comment points out, that 20" screen is a lot easier to use to edit such parameters than an LCD. The computer allows me to feed through my MIDI mixer/merger; the computer allows me to see a wave form in a sample, cut and fine-tune loops, EQ points, etc.; it allows me to see and edit MIDI events; and, when I'm all done, the computer also lets me mix and feed through my DSPs to hear, and eventually master, a major mix.

Expandability of the MotifES was one of it's selling points. My mLan is, as Yamaha advertized, the "missing link," at least for me.

The other side of this equation is the fallacy of an "All-in-One" solution: often this means a device does everything so poorly that it's a waste of time and money. I don't want to play riffs on my computer keyboard, and I don't want to edit waveforms on an LCD screen. I do want to integrate sound modules and sample memory into my instrument, and I do want to enhance the ability of my devices to communicate with each other.

In sum, I think that the choice comes down to the needs of the user: if what you need is portability/mobility for performances, put it all into one package and take it away. If you need to bring multiple components together, and/or to edit elements, you need some device that allows such flexibility--and, as of this writing, that means the computer.