I have a pair of peltor 7s and ProMag Dimension 1's. Both are good, the peltor's are a little less expensive. Both have roughly the same NRR, but I always wear ear plugs + the muffs for max protection, since I do most of my shooting at the indoor range. You can still hear well when double plugged.
Peltor's - Good, they do "clip". Its only a problem if there is continuous shooting and you're trying to hear someone speak, then it cuts out a lot. If you're going hunting, then it shouldn't be a problem. They are comfortable and they do amplify sounds.
ProMag's - they "attenuate" the sound so the volume is automatically turned down but you can still hear (albeit at a reduced level). I like using these at the indoor range since you can still hear the range officer, etc. I use the ProMags all the time unless I take a newbie to the range, then I give them the ProMags (safety reasons). These cost about $50-60 more but I like'm.
I've also had the batteries discharge too. The little foam covers over the microphones sometimes get knocked off.