Meh. Legato on guitar comes at a cost of expressiveness and note choice. When hammer-on and pull-off are your only ways to sound a note, you lose all the coloration available from dynamics, palm muting, distance from bridge, pick angle, and the million other little things guitarists do to make a note special. And note choice? Scales of any substance will force either difficult position shifts, or legato-breaking string switches.

It can be done, and I certainly do it. But it can't be all that's done, or your sound falls flat.