The Shifty is essentially a combination of four sample and hold stages, a sequential gate and sequencer controller. This collection of functions allow for some specific and useful utility application.
One of the primary uses for Shifty is to take a monophonic sequence source and route each new note of the sequence to up to four different synthesizer voices in a specific pattern. In this way you can create pseudo polyphonic sequences since each voice can be triggered to play and sustain while the next voice int the sequence gets triggered. Another term for this is hocketing.
The other main application of the Shifty is to function as an Analog Shift Register. In this mode each new gate input received causes the current set of pitches to be shifted to new output locations as a new one is added and the oldest one is replaced. This can be an interesting way to create chords that are up to four stacked notes when used with a pitch sequence source that has a harmonious series of notes (e.g. a pentatonic scale works really well). Even just using two of the outputs will yield very interesting melodic interplay and is an excellent way to make a simple sequence much more complex and interesting.
In a more basic way the Shifty could be used as a simple Sample/Track and Hold module or as a sequential gate.