Hi, Callie!
I've used MIDI SuperTracks a few times

LOVE THEM!
As Mario stated, they are great when a comparable RT would be stretched a bit much... and the ability to use VSTs of your choosing is terrific - allowing you (the user) more control over the sound - I particularly like that for the pianos!
Here are some songs (in the Showcase) that I found that I have used MIDI SuperTracks - typically pianos or strings...
UP TO NO GOOD AGAIN
2060: Strings, Rhythm PopCountry Ev 120 - Hi-Q 049 01 Strings, Ensemble, Chamber SampleTank.tgs
2060: Strings, Rhythm PopCountry Ev 120 - Hi-Q 050 01 Strings, Ensemble, Movie SampleTank.tgs
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=232231#Post232231THE DANCE OF A MAN IN LOVE
MIDI SuperTracks in song: 2058:Strings, Rhythm CelticAir Ev 085
MIDI SuperTracks in song: 2060:Strings, Rhythm PopCountry Ev 120
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=240876#Post240876I WISH IT WAS MEANT FOR ME
MIDI SuperTracks in song: 2066:Piano, Rhythm NewAgeAnswers Ev16 110
Hi-Q 001 01 Piano, Acoustic, Grand SampleTank.tgs
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=245523#Post245523CHOKING
MIDI SuperTracks in song: 2066:Piano, Rhythm NewAgeAnswers Ev16 110
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=253410#Post253410DO YOU REMEMBER
MIDI SuperTracks in song: 2060:Strings, Rhythm PopCountry Ev 120
MIDI SuperTracks in song: 2058:Strings, Rhythm CelticAir Ev 085
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=260854#Post260854REAL LIVE COWBOY
MIDI SuperTracks in song: 2066:Piano, Rhythm NewAgeAnswers Ev16 110
MIDI SuperTracks in song: 2254:Piano, Rhythm CountryBalladJohn Ev 120
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=272556#Post272556HOLD ON (JANET'S SONG)
MIDI SuperTracks in song: 2066:Piano, Rhythm NewAgeAnswers Ev16 110
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=275325#Post275325SHE DOESN'T CARE
MIDI SuperTracks in song: 2066:Piano, Rhythm NewAgeAnswers Ev16 110
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=284961#Post284961BETWEEN THE PAWNSHOP AND THAT WOMAN
MIDI SuperTracks in song: 2248:Piano, Soloist CountryShuffleJohn Sw 120
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=297244#Post297244ANOTHER CURVE
MIDI SuperTracks in song: 2066:Piano, Rhythm NewAgeAnswers Ev16 110
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=300259#Post300259HALF
MIDI SuperTracks in song: 2231:Piano, Rhythm 80sPopBallad Ev 085
MIDI SuperTracks in song: 2058:Strings, Rhythm CelticAir Ev 085
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=303800#Post303800YOU'LL NEVER FALL IN LOVE AGAIN
MIDI SuperTracks in song: 2058:Strings, Rhythm CelticAir Ev 085
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=308974#Post308974Thanks! Don't know how you do it, but...
KEEP 'EM COMING!!!!!
floyd