I have one on my GSXR1000 track bike and love it. However saying that its only really needed for track use unless you have a disability which makes using the rear difficult.
On the track i find it useful mid corner cranked over, applying the rear can tighten your line slighty if you drifted out. Also good for draging to keep the front down on the 1000, probably not alot of use on a 250 though.