When loading Audio Snap, I continually notice bpm on material to be significantly off, even when on a single track. Conversely, I have played with some VSTs recently which can very accurately pull bpm from commercially-mixed material which is heavily limited. The only "difference" I can see from these two situations is that the VSTs are using an audio microscope (high-Q EQ band) to isolate the bass end of the spectrum. It "seems" that Audio Snap threshold is linked to volume alone, which is a pitfall (and on commercial material falls apart readily).
Feature request - To include a high-Q, EQ band in the "Threshold" settings on Audio Snap which can be adjusted by the user to isolate transients more accurately.