Amazing! It took about 20 minutes to go over most of our bedroom ceiling and find all of the studs before we put in some downlights. I put a bit of tape everywhere it stuck and after about 10 minutes it became obvious what the spacing was and I could zoom through the rest of the room.
The photo was taken just before I moved the bed so I've covered most of the room except the part by the windows.
My tip would be: hold it very loosely between your finger and thumb as you move it around, that way you'll feel and see it pull as soon as you get near anything metallic.