Anybody ever used one of these

http://www.wiggle.co.uk/ctc-plastic-bike-bag/

Would you risk it?

Yep. On a coach. Not sure I would on a plane though.

Hi,
I used one when flying to the Alps with my road tourer a couple of weeks ago. It was fine on the way out, no damage, on the return journey the front wheel got a bit out of true, still rode fine with rim brakes though, so not a big deal.
Definitely helped it being seen as a bike not another bag to throw around, both journeys I saw my bike being loaded up and it was always on the top of piles and left until last to be loaded onto the plane.

Hope this helps, it was definitely worth it!

Joe