It was a great time saver for rehearsals. We could loop a section of a song we wanted to work on and everybodys patches would just work. Or jump to another song and we didn't have to wait for the guitar player to go fiddle with his FX and wait for someone to go change the synth patches and electronic drum patches... it was cool for the show, but even more efficient for rehearsals. Plus the tempo was given as a count in automatically so everybody was ready at the press of a couple buttons.

In the beginning we actually ran the show from a sampler/sequencer (W30) so I didn't even have to leave my synth to jump from song to song. At that time we used the computer to record the performance (audio) and act as an extra synth via the soundcard. The sampler loaded the whole show from two floppy disks.

Since we only had 16 tracks available on the synth many times a track would have more than one MIDI channel of data on it. For instance the guitars would share a 'Track' with a Yamaha FX box that was set to receive on MIDI channel 14 while the Boss FX box was set to receive on MIDI channel 15. So that track went out thru the Boss (which ignored channel 14 and used 15) then into the Yamaha which used 14.
With the added level of tracks-to-ports there are ton of possibilities on how to use MIDI.

In the studio -
When recording a CD we did the same thing pretty much. Because we saved the patch settings along with the audio and MIDI recordings it was very easy to punch things in.
Example- guitar player decides a week later he wants do a part differently. Hook him up and hit record and his FX would change to exactly what he used previously so he could concentrate on just playing the parts. Plus it is a reference of the data for when you go play the songs live later on. None of that "which patch did I use here?" stuff to deal with...
Make your sound your own!