They are pretty comfortable, though they take getting used to because the seal is perfect and you'll slightly pressurize your ear canal which is a strange feeling. They'll also fit slightly inside your ear, so lying sideways is fine.

The downside is they're very expensive, relative to other earplugs and mine no longer seal as well as they used to so I'd need to get a new pair. They're still better than nothing. I started using earbuds around the same time, from using cans, and I wonder if I've very slightly widened my ear's opening.

I also use an eye mask if I'm somewhere that doesn't have good curtains or blinds. Really works very well, but I recommend one that wraps around and doesn't have an elastic band to dig into your ears (Matador makes a good one).