There are certainly a number of ways to experience Torres del Paine, and hiking the W trek with Ecocamp turned out to be fantastic way to experience the park. We booked the 7 day trek, whereby you stay 4 evenings in the Ecocamp domes, and 2 evenings at the refugios (hostels). We had a suite-dome which was super charming and unique, and the view of the TDP from the dome makes it feel that much more special. The guides and staff were very helpful and attentive. All together, a well organized and pleasant experience and would definitely recommend.
The refugios you stay in during the multi-day trekking excursion are very basic and, to be honest, I wasn't looking forward to a shared room with 6-8 people. But after some time together trekking in such a beautiful location, you bond with your fellow trekkers and it becomes a camp-like experience and was actually quite fun. Make sure you a bring a quick-drying towel (we picked one up in Puerto Natales) as you'll need it during the 2 evenings at the refugios.
We also booked the big-ice extension at the Perito Moreno glacier. Definitely worth seeing and, at the end you get to drink whiskey with 300 year old glacier ice! Best whiskey ever! The border crossing into Argentina is slow, so just remember it will take 6 hours to get to El Calafate.
We also spent a few days in the lake district (Frutillar) to see the awesome volcano (Osorno). The German influence around this area is interesting and worth a visit. I would visit the lake district before the trek, because you can't fly from El Calafate to Puerto Montt directly, which means we had to take several buses to get back to Punta Arenas before catching our flight to Puerto Montt. One word of advice, there is really not much to see or do in Punta Arenas.