My first acoustic was a Yamaha 12 string. It sounded amazing & I was glad to have it. However if I had the choice now I wouldn't have picked it as my first guitar. It's no different than playing a 6 string but it's really hard to fingerpick.
Tuning is a bit of a pain but you get used to it.
The only real negative thing I found was that Yamaha recommended that you tune the guitar down by one step so that there wasn't so much tension on the neck. I did this for about a year but got tired of using a capo all the time to play in standard tuning so I eventually just tuned it up to standard.
About 6 months later the whole bridge had started to pull up and there was a noticable warp in the guitar body. The strings were way off the fretboard too so you couldn't play it in tune anymore.
The only reason I'd use one now is for the sound. There's a certain sparkle you get that you can't duplicate on a six string.