I have one of these on my bike, bought it from my dealer the day I picked up the bike, and put it on a couple of days later. (dealer =
http://www.woodfordmotorcycles.com/)
Good is:
1) easy to carry.
2) hard to forget to take it off.
3) easy to fit.
4) as a footpeg it is easy to get on and off, and feels plenty secure when it's locked in place. As a lock, no idea, haven't seen any stress/time to break tests.
Bad is:
1) it doesn't seem to be wearing very well.
The slot where the key goes faces forward when on as a foot peg. It has a little slider to cover the hole, but that seems to come open sometimes, and water and grit get in anyway.
The rubber seems pretty soft, and is looking very scuffed and worn after only a month/1000 miles.
2) It's considerably wider than the standard peg, and maybe a little longer.
This means when moving the bike, I tend to hit the side of my leg on it.
It's a lot harder getting the heel of my boot between it and the center stand to deploy the side stand.
I've actually been thinking of taking it off, as I'm worried that the lock will jamb before to much longer.
I think the idea is very good. The adaptor works well and it fits well.
It would be better if it was narrower, and the keyhole faced rearwards (or outwards) in peg mode, and the rubber surfaces were harder/tougher.
Cost from memory was about £50 including the adaptor.