I use the greenlee version, doubles as a regular level too.

[Linked Image from news.thomasnet.com]

The bubble is really sensitive though. That is the only drawback it has for me. Besides making bending easier, It just doesn't take as long to get the other side of the offset to line up. Just level it back out and bend away.

"If common sense was common, everyone would have it"-not sure, someone here