Yup - I bought two of 'em...
They're still in the box under my desk at work.
I've found that I can move my seat back, pull the belt tight and flick the top of it so it locks, then move the seat forward. This (so far 2 autox and 1 school this year) has held me in the seat pretty well... Others may have a different opinion. I will eventually put them in my car to see if they work, but the seatbelt trick seems to work pretty well too. Just my $.02