I did the Selvaggio Blu hike. I signed up for 7 days plus 3 extra days to see Cala Goloritze, Cala Marilou, and Cala Luna.
I am an American. I can do hikes considered "hard" in the U.S. and I have experience rock climbing in the U.S. However, nothing I did prepared me for how hard the Selvaggio Blu is. The SB is steep incline up and done rocks, some of which are lose and you can slip and fall at any given time. Also, you have to sleep in the wilderness and they feed you cake in the mornings. Americans are used to eat hearty breakfasts even we do not go on a week-long hike. I had little energy eating cake for breakfast and not being properly prepared for the hike.
I had to be sent home 3 days early. I was worried they were going to bill me for time lost and tell me that's my problem. It was so refreshing that they did not. It left me with a good impression of Sardinia.
This whole trip was well organized with all the details covered, like with trash collection being brought back by boat. However, since Sardinia is on the cusp of a tourism boom, esp. from the Americas, be warned you may not be able to complete this hike. Also, it was unnecessary to book Goloritze and Marilou as separate days bc they were included on the 7-day hike.