I recently picked up a ten pack of Martin & Co 13/56 Medium Bronze acoustic guitar strings after I saw them on sale and I have to say that I'm really happy with the purchase.  I usually get light bronze Martin strings because I have smaller fingers and they are easier to play for acoustic, but since these were on sale I decided to try them out.  While they are a little tougher to play at first because of the bigger gauge, after playing them for a few days I've definitely gotten used to them and they are now quite easy to play as well.  The best part about the Martin & Co 13/56 Medium Bronze acoustic guitar strings is that they have an immaculate sound to them that is extremely full and rich sounding.  I got a similar sound with the ligher strings made by Martin, but I guess the extra size gauge gives them a little extra to their sound.  I have played two different acoustic guitars stringed up with these - a Martin DX-1R and a Taylor 814-CE and both sound really great with these strings on them, which is not to say that they probably wouldn't sound great with any strings, but it is noteworthy that both guitars of two different brands with the same strings both sound great.  Since I got these on sale, the price was truly a bargain, coming out to about $3 USD a piece in the pack of ten!  Even though this was a sale, if you buy a ten pack anyday you can still get a pretty good deal and even if you buy a single pack the price isn't too expensive.  While I still prefer lighter strings, the Martin & Co 13/56 Medium Bronze acoustic guitar strings do a great job and I would highly recommend them to any aocustic guitar player.