I am a recent convert to sleeping in shelters when backpacking on long distance trails. Before that, I would always bring an enclosed single person shelter, like a hammock or a tarptent, but 4+ inches of rain on Vermont's Long Trail over a three day period changed my mind. Trust me, you can adapt to the invasion of your private space and snorers when it is raining cats and dogs. Plus the rain acts like a big white noise generator.
Even if you plan on staying in shelters, it is important to bring along a fall back shelter system in case a shelter or hut is already full or if you run out of gas between between shelters. I'm addressing this by bringing a tarp, which will let me shave some additional weight of my gear list, trading in a 28 oz tent for an 11 oz tarp and a 3 oz bug net. This is a big weight reduction for me and will bring my base pack weight under 11 lbs.
I've been using tarps for a few years as a component of my Hennessey Hammock sleep system so I already own a few. But, the following video from Mike Lummio at bushcraftnorthwe st.com provides some great tips about how to set up a tarp on the ground. For me, Mike's use of a standalone ridge line and prussic knots is great advice which I'm going to implement on my next section hike when I have some time to kill at a shelter and can sit around and set up the knots. The prussic knots also prevent water from running down the ridgeline and dripping onto you when it is raining.
Do you sleep under a tarp regularly? What kind of tarp do you use?