I mainly blip at slower speeds (suburban residential type roads) to try and match the engine and drive speeds when re-enagaging the clutch, for a smoother slow-down for traffic lights or to take a corner.
I am under the impression that this also extends tyre life (as compared to letting the rubber do that job).
Blipping when out on the highway or gearing down for sharper turns on mountain roads also helps the tyre keep its maximum traction when the clutch is re-engaged.