I too am a floater. It is much quicker and like PaperPrincess, I like access to the back of the quilt. For minor adjustments I will pin the sides to the backing and baste the sides before attaching the side clamps.
That being said if the quilt is not square or is some how wonky I will use the traditional pinning method which allows a bit of finesse!!
Cindy - I am intrigued with what magnets you use from Harbor Freight - my DH often goes there when we are down near the store - it is amazing what can be repurposed fro sewing from there.