Sling strap you're really happy with?

Anyone using one of those cross-shoulder sling straps--the ones that attach to the tripod socket?

Brand names Joby, BlackRapid, Op/Tech, variety of others ...

They seem to go for anywhere from $10 to $80+ dollars, just wondering what to stay away from with the cheap ones, or what makes the good ones worth the money (other than feeling secure about what's holding my camera up). On that--any issue with the camera dangling by the bottom plate rather than the 'real' strap lugs?

Thanks,

bob