The biggest issue with double tracking acoustic guitar is the differences in strumming really show through (more than electric guitars, IMO). It takes a lot of work to get the 2nd track to match up with the first one unless its' a slow consistent strum style - flourishes and fast upsweeps for accents can really give a phased sound when they don't match.
I agree with Pinky - DI seldom sounds good, but it does depend on the pickup system. Most have a quack that is hard to dial out with EQ. I have used it to add a little mid-hi "bite", but have found that its really better to not use it at all.
The only "real" reason to have a stereo track (2 mics) on an acoustic is if it is a solo instrument (with no more than 1 vocal with it). If that's the situation, and your room is well treated, mid-side is the best way (IMO) rather than X-Y of two matched mics.
Even when I use 2 mics, (one at 12th fret aiming slightly towards the soundhole, one at lower bout) I pan them together, or just a few degrees apart.