I've placed mics everywhere. Different types of mic in every possible position. Yes, it does make an appreciable difference to the sound of, say, a guitar (eg a mic placed directly in front of the soundhole sounds very boomy, to the right near the bridge sounds a bit more mid-rangey, to the left pointing at the 12th fret generally sounds the most balanced).

But the overall insurmountable sound remains the same, a kind of boxy muddiness. It might not sound too terrible on its own, but the second you compare it to any CD in your collection (or even the majority of home-recordings on soundcloud/bandcamp etc) it sounds pretty terrible.

In fact (for a limited time only folks!) you can actually hear me trying a microphone in different places, both strumming and fingerpicking, on my Maccaferri guitar.
And also different vocal mic'ing positions too (above head, directly on, slightly below chin facing up). This is cos it's an obscure mic and I'm trying to sell it, figured I'd give any potential punters a (very, very, very rough) approximation of what it could sound like in a decent room.

can be heard here: KVG Aardvark microphone test on guitar & vocal (Let the Mermaids Flirt With Me)