As a firearms instructor and competitive shooter I have quite a few sets of noise cancelling headsets...in general, I love them. I wear them pretty much any time I'm running my tractor/mower/backhoe/snow thrower/string trimmer/etc. I like that they give me the ability to hear if something sounds weird, if someone is yelling at me, etc.
I have three sets that I wear the most. For tractor work I normally wear a set of MSA Sordin Supreme Pros. I love the electronics on them, and I added gel ear seals for comfort, but for some reason they start to bother me after 4-5 hours (which is why I stopped wearing them on range days). For shooting I have a couple of other sets. One is a set of Peltor Tactical Pro that I wear the most for shooting and instructing...comfortable all day long. They are the bulkiest, but have the best dB reduction. I added gel ear seals and they're quite comfortable. They don't work well for shooting long guns, so I wear a set of Pelter Tactical Sport that are much lower profile, and still have decent attenuation...need to order a set of gel ear seals for those one of these days since they really do make a difference.