I have one in 4m (my profile pic)
Works well, it needs at least 15 knts to be able to takeoff but i dont have a good pumping technique with my legs as i am on a new board (still getting used to) or a compact freestyle board that sticks to the water.
D?cent d?power, I could ride it in gusts around 25 knts i think, but with harness only (it pulls a lot on the forearms). Its very stable in the air. Pretty r?active also i managed to jibe in my first session, trying the tacks now and managing to pull some (its my first time tacking as i only jibed when winging but i think someone used to tack a wingfoil will tack it no problem). Im very happy with it after 5-7 sessions (2 in perfect wind, 1 in 5-28 knts, and three in lighter conditions)
Keep in mind i have not tried any other brands.
Here are some pics, the one with the GPS is to show the angle upwind (i was not trying to go upwind very hard, when i did i was going upwind as well as wingfoilers, in between 50-60? of the true wind angle)