I have ~1/8" at the 12th on my faded special, a little lower on my Standard. I prefer my action on the low side, the standard is just about perfect. Both guitars get some rattle when unplugged, nothing the amp picks up but it's still annoying to me. These guitars seem to take quite a bit of tweaking to get them lower than 1/8", I suspect it has something to do with the set necks angle to the body.
All guitars are different... even within the species. So what's good for mine may not be good for yours.
Set your action as low as you can stand it without buzzing - if that's your goal. Measure it if you want, but in the end you can only adjust it to where it works for your fingers and your particular guitar - it's gotta be useful. Don't forget to adjust your pickup height as well - unless you like string slap.
I like my action low on my Gibsons (never measured it) and medium high on my Strat. The distance from the fretboard and pickup has a definite affect on the tone.
"Officially" (ha-ha!) action is low at the 12th fret (treble) at 1.2mm, 12th fret bass 1.6mm. Then we have (respectively at 12th fret treble and bass again) medium = 1.6mm and 2.0mm, high = 2.0mm and 2.4mm, and slide = 2.4mm and 3.6mm. In each case this is from the top of the fret to the underside of the string.
My Standard was set up superbly from the factory at a low action (in contrast to many set-up horror stories I've heard) and just the right neck relief (I'm a light player so don't need a lot). I prefer a medium action though (easier for bends) so I've raised everything a bit.
My question: why do you want to go as low as you can go? :coolsmiley: