pros: the location is great not only for hipsterish and touristy san telmo, but the nature preserve next door, which is a great place to run or bike away from the stress of Argentinian paperwork and the calories of buenos aires food.
cons: the bed is remarkably narrow, although the only solution to this, given the space, is to substitute some sort of folding couch to replace the sofa. Also, the window view is not exactly breathtaking.
On the positive side, it is quiet. Also, the bathoom is very very nice, (particularly by local standards), nicely finished and the shower wont freeze or burn you. And the folks running the place are perfect: responsive and helpful yet not nosy or obtrusive.