The best use right now IMHO is capacity leveling at the grid level. With a VRB, an electricity provider can downsize its capacity from supplying peak levels from a generator and instead run 24/7 and dispense power at peak from the battery stored at off-peak times.
Actually there are lots, but this is the one that will have ridiculou$ benefits.
The VRB for large scale wind storage seems like a bit of a red herring to me as many of those wind projects tap directly into the grid anyway. On a residential level, it makes sense though.