Gorgeous, steep line up a corner. Short bolted crux @ p5-ish. Mostly fun, steep, moderate climbing. Mind-blowing setting.
The crux is followed by some lower-angle climbing on lower quality rock before getting back in another steep corner.
Rolo Garibotti's Pataclimb.com lists the route at 6c+, equivalent to 5.11b. This might be true if the crux were full of ice or something; otherwise it's noticeably easier than that.
Pataclimb says of El Mocho: "Its easy approach, its low elevation, its incredibly featured good rock and its protected walls provide some of the best free climbing terrain in the whole range."
Rap the route to descend. The first rap down a chimney to the immediate left is a rope eater--but it's a fun 5.9ish chimney if you have to go back up after your rope. Can be rapped with a single 60m if you're willing to leave a small amount of gear or rap off of dicey tat.
On the north face of El Mocho, at the base of Cerro Torre.
The approach/descent to/from Niponino is a pain in the ass, but easy and short by Patagonia standards. Descending the wet slabs is tricky in the dark--consider rapping the steepest parts if there's a lot of water. (There are minimalist anchors here and there if you wander around long enough.) Pay attention to the route finding on the talus and slabs on your way up.
Niponino to Niponino is 20 hours max at a leisurely pace. Strong parties that nail the approach/descent will be much quicker.
Double Camalots to #3; optional single #4. Route takes good med-large nuts and they're useful for beefing up rap anchors; 1 set is plenty if you don't mind leaving a few. Some webbing and rap rings will likely come in handy if rapping with a single cord. Inspect all rap anchors--you're not in Yosemite!