My 2 cents...
I recently spent time up at a noisy cabin. It was fun, but after a while I just wanted to zone out with my own tunes; and I was glad I brought my Etymotic IEMs (ER-6i). I feel somewhat disappointed regarding their sound quality since they lack deep bass, but they did do a pretty good job of blocking out everyone else's partying. It's not that I couldn't still hear other people (somewhat), but it definitely muffled sounds enough to the point where music was easily enjoyed.
I've also found they help when riding in a car to drown out highway noise, but they are no match for if someone turns on the car stereo and has the volume loud.
One thing I don't like about IEMs is that they will inevitably get ear wax on them. And they take a little bit of getting used to as far as being comfortable with having them in your ear canals.