I don't really use them but listen to enough songs with them in them and have noticed that a sweep would be more like a "Metal Turnaround" vs. a "Blues Turnaround".

Like MP said it is a good "tension" builder. So to use in ipmprov try to stay toward the "end" of the chord progression or if you feel you are running out of ideas--while soloing-- A good sweep followed by a sustained note or bent note can buy you some time.

2 cents.