To look or not (or how much)

[StringFive]

I think you want to work to get to the point where you don't need to look...at least all the time. It's important to have that intuitive feel and so I coach all of my students to put playing naturally and freely...often without looking...at the top of the list of their playing goals.

[GrayPlayer]

Try running scales or just doodling without looking.

[cmd612]

One other point I don't think anyone has mentioned - if you sing while playing, looking down can interfere with breath control and vocalization. Depending on the style of singing, this might matter quite a bit or not at all.

[TBman]

Once you're playing a couple of hours a day for a couple more years after a while you'll probably play a lot without looking. It just comes naturally.

[stanron]

Originally Posted by cmd612

One other point I don't think anyone has mentioned - if you sing while playing, looking down can interfere with breath control and vocalization. Depending on the style of singing, this might matter quite a bit or not at all.

This is a good point. When I sing my playing is pared down to little more than dum chink style. However this is more to do with focusing my attention on singing than any thing else. If I try fancy guitar work while singing my it's singing that suffers.

Having said that, I stand when singing and playing. In that position I can't see the fretboard anyway, without leaning forward. As someone else has commented, that's where the edge markers become useful.