I got into the MIDI guitar thing a few years ago and started with a Roland GK-2A equipped
"Roland Ready" strat -- simply a Mexican Strat with the MIDI pick-up fitted into the pick
guard -- and a GI-20 interface. A few weeks of headaches and frustration with the MIDI
end were always offset by real fascination with the sounds and versatility of MIDI
triggering. There is a real learning curve to getting a handle on the rather arcane MIDI
language.
After a few months of this I stepped up and bought a Brian Moore MIDI
guitar with the pick-up incorporated into the bridge. This made a huge difference in the
precision and playability of the MIDI.
MJC makes the very valid point, however,
that trying to play piano from your guitar will force you to concentrate on very precise
playing, or else drive you mad.