I'm trying it now... Pretty mixed results. Low brasses and synth sounds (of course) sound good, drums sound decent. Complex songs of course cause note clipping. Volume balance of some instruments seems off, with some instruments totally overpowering others. Drums are pretty good, but I think that MT-32 drums are mostly GM compatable already? Wind instruments sound slightly below average for a General MIDI synth. Strings are average.
As Kippesoep mentioned, the piano still sounds like a stringed instrument and not a piano, as is normal with the MT-32. I guess the MT-32 must have been invented in the days of Bach, when everyone was playing harpsichords (like pianos except they pluck the strings instead of hammering them) and the piano hadn't been invented yet 😉
I didn't notice any obvious missing tracks in the songs I tested, which is interesting considering the MT-32 doesn't normally seem to play anything sent to it on MIDI channel 1 (interestingly, one of the previous owners of my MT-32 sold it on eBay because he couldn't get a MIDI keyboard to work with it for this reason; I was able to get it working by using MIDI-OX and/or Cakewalk and mapping my keyboard's channel 1 output to one of the MT-32's channels 2 through 9 inputs)