I have not used audio snap in sonar,,,, however, I have used the audio stretch, shrink, and more in Melodyne.
I had a sax note at the end of a song that was too short.....it needed stretching on a hold.... it worked excellent.
I have also used the move a note where perhaps I was early or late to the note..... melodyne let me drag it right where it needed to be.
You can also use it to edit out notes, breath noises, etc.....
I have also used it to separate the notes, also change the pitch curve in the note, and more.... it is a very useful tool. removing the pitch variations is one of the most useful things that I have found....since I tend to overuse vibrato and ME allows me to take it out to where it sounds decent.
As was pointed out in one of the videos, it will sometimes connect 2 different notes into one. It's easy to split it out and move each where it should be....editing the internal parameters of the note to keep the result totally natural sounding.
I love that thing.