Time stretch can be up to 1 million times slower. Pitch shift is plus or minus one octave. Blurring blends nearby spectral material to make the output less static.
Playback is sensitive to transients in the source material. Playback rate and blur amount are automatically adjusted according to the transient contour of the material being stretched. Playing transients at a faster rate than non-transients tends to make the output sound less obviously stretched. Playing transients more slowly than non-transients emphasizes the stretchiness[good when playing in reverse mode with highly transient material]. Adding blur brings in some subtle (or not so subtle) randomness which helps to keep the output less static.
tcStretch is on a beta phase, please contact the author if you have any issues or suggestions.