These hearing protectors are excellent devices for shooting. They provide a stereo sound-view of the world around you while keeping any loud sounds from affecting you. They are quite comfortable (though I have yet to wear them for long stretchs it seems like they would be fine over an afternoon). They are 1000% better than my previous hearing protectors, which were not electronic (I wouldn't go back).
The only thing that is annoying is that they advertise an "Audio jack" for "cell phones, MP3 players or dog trackers" but it is a completely non-standard (and mono, not stereo) port on the device, and the audio cable is not included. The audio cable is very simple (costing less than $0.50 to make, is my guess) and I found it selling from $22 to $40. What a crock. I'll have to check at Radio Shack to see if I can get a compatible cable for a reasonable price.
For shooting I can't actually imagine using this connected to an MP3 player as I usually want to know what's going on around me. However, I can think of other uses for this muff where I might want music as well (mowing the lawn, using a leaf blower, etc.), but not badly enough to pay another $22.
Peltor: Include a cable in the next version, or better yet use a standard 3.5mm mini stereo plug and provide or sell an adapter to the "old" two-prong plug!