The "W" trek is touted as one of the great treks in the world. We were there in January, 2013, and it lived up to its billing. The central massif rises at least as dramatically as the does the Teton range in Grand Teton National Park, soaring at points well over 2000 vertical meters from the land below.
We stayed in refugios, which were clean, quiet, and not (like some European alpine huts) cramped. Food was adequate, and beer/wine available, admittedly at ballpark prices. (One refugio had a bar whose view was better than I've ever seen from any watering hole in the world) Camping was available proximate to the refugios, and at other points in the park, as well. The landscape, including the towers, glaciers, the iceberg filled waters of Lago Grey, was beyond description.
At it was high season, trails were reasonably crowded, but not unbearably so. People we met ranged from 20 something "vagabonds" to families out for day hikes to numerous "mature" walkers like ourselves.
It is a major production to get to this part of the world from the Northern hemisphere. You fly to Punta Arenas, and then must arrange transportation North to the park, several hundred kms away. (We used Dittmar Adventures, a local company, to book our trip, and they did a fine job).
However all the grief and cost of transportation pales with the experience you will have. If you are a reasonably fit hiker, it is very doable, and NOT TO BE MISSED.