Hovarter has developed a clever approach to the leg vise which in their new VX20 mechanism. It appears to consist of a purposed precision shaft coupled with a special linear bearing which permits free travel until engaged by rotation. This allows the user to quickly engage the work piece just by pushing on the chop and, once in position, a few rotations provides clamping pressure. The video explains the concept (there's also an article up on Chris Schwarz's blog\Popular Woodworking, which is where I found out about it):

Hovarter Custom Vise VX 20 Introduction - YouTube

Things get really interesting when you consider the combination of the VX20 with the linear bearing parallel guide replacement approach shown here:

Roubo Workbench Leg Vise Alternative – Linear Bearings | The Wood Whisperer

There's the potential for a cool peg-free, quick-engage\release setup here. The VX20 is due for release this spring (Aussie) and, at US$140 it may not break the bank like some of the alternatives.

Any leg fans currently building or preparing a bench build interested in this approach? I'm going the linear bearing route myself, but having seen this I'm tempted to forgo the thread for a VX20. Guess we'll have to wait until later this year to see if it lives up to expectations.