i thought i'd drop in with another thought (i already voted like years ago, lol) and btw, i'm in the "it takes 1-2 seconds crowd", except the obvious open strings, 12th fret and certain other "home" notes i use more often (which includes all of 6th and 5th string notes and then their corresponding octaves on 4th and 3rd (that's how i know those, helps on bass too).
anywho, recently in our band we've been trying to add a horn section (all just friends jamming together, no pros) and since trumpet is a Bb transposing instrument and alto sax is Eb, knowing the notes on guitar helps me almost instantly transpose notes and keys - for trumpet it's a major second up, for alto it's the same fret as trumpet on the adjacent lower string - they were surprised at how fast it takes, but it's not me - it's all the guitar (and its tuning). musicians who play most other instruments (except similar string instruments tuned in 4ths) just don't have that sort of visual "interface" to various intervals in music. Even on a piano keyboard it's not as easy to find even a major or minor third of a note, but on guitar it's always "visible".
sure, guitar's "standard" tuning lends itself to being easy to learn without knowing notes (just memorize patterns), but coupled with knowing the notes, even if you're not the fastest player, you can really be a musician, not just "player".