Well, just bought some. So my comments.
First bought the Givi Airflow 330. Well worth it. Reduction in wind noise and buffeting around the head make the bike even more of a pleasure to ride.
But, I got more buffetting either side of my body (feels like alternating vortices hitting you).
Winglets have stopped this side to side buffeting completely.
In summary if you do many motorway or dual carriageway miles, then yes, worth getting. IMHO of course.
Chris