It has very little combat usage, there's a reason the Raptor doesn't do it. Any time you see an aircraft do some high AOA (Angle of Attack) maneuver and provide almost zero line of site (not moving up / down / left / right), you know he's slow and you've won the fight if you have airspeed (assuming gun only).
The only benefit would be to get an IR missile off when you've already realized you are losing and he's behind you.
This made me smile. I really don't recommend actually doing this in real life for a number of reasons, but how totally epic it would be is very much not one of them.
JHMCS isn't that useful in such extreme off-axis situations. A missile taking a big turn requires it to expend a lot of energy and drastically hampers its probability to hit the target.
The only benefit would be to get an IR missile off when you've already realized you are losing and he's behind you.