Okay, I've been reading this thread, debating on whether or not to throw my $0.02 in. Those who know me know that I never miss an opportunity to share my opinion, so here it is.
I presently own two headsets, a PNR set of DC's that I bought for $295 when I first started my training, and a set of Bose X's that were given to me as a gift when I got my PPL. Both work great, and I love the ANR in the Bose (my girlfriend has even joked about grabbing them from my flight bag at night to battle my snoring when I forget to put one of those Breathe Right strips on - those things have saved my relationship). Now, I've had the opportunity to try several other types as well (my mentor has quite a collection).
I forget the brand, but I tried one set of his that was an in-ear ANR headset. Maybe I couldn't get a proper fit or something, but although it was fine on the ground, once I applied take-off power and was climbing out I couldn't hear the radio or the intercom. Fortunately, that was a dual flight with my CFI and I had him take the controls while I grabbed my trusty DC's out of my flight bag. I've tried a couple sets of his Lightspeed ANR's, and I really didn't notice much of a reduction, and those cups were so huge I kept banging them on the window of his Bonanza. Also, while he was on a hiatus from flying while recovering from back surgery, he let me borrow his DC X11's for a while. Those were great compared to my PNR DC's! But, now that I use the Bose, they weren't nearly as good.
Besides being expensive, the biggest criticism I hear about DC's is that they are "head vises", and clamp on really tight. I have a very large melon (to the point that when I buy new sunglasses, I have to search for quite a while to find a pair that fit me right) and I've never had an issue with them being so tight as to cause discomfort, even on my longer X-C flights. I do know that they seal tight because (at the risk of grossing people out) there were times after practicing Touch n Goes or low airwork in the summer I would take them off and sweat would just pour out of them.
About a month ago, I took husband-and-wife friends of mine for a $100 hamburger. On the first leg, the wife sat in the right seat and used my DC's, the husband sat in the back and used a POS ASA rental set from the FBO. They switched seats and thus used the other headset on the way back. After we landed, they both said that they liked my DC's much better.
The bottom line is that you could probably get a decent set for <$295, but don't just go for the cheapest out there, because there is definitely a difference in quality. Also, whatever you get, make sure that it has a flexible "gooseneck" style microphone booom and not an articulating wire one. The screws at the articulations get loose and the mic keeps falling away from your mouth until you can find a small screwdriver to tighten them again. This isn't an issue with the goosenecks.
And now for a (somewhat) related story:
Last month at the museum, the Wings & Wheels theme was Cessna Day. One of our board members brought his C210RG in for the day. I didn't notice it when he came in, but when he left, I noticed that he didn't use a headset. He had a boom microphone that came down from the roof that he positioned in front of his mouth, and I guess he just used the cabin speaker. I had never seen anyone do that before. I also noticed that he didn't put any kind of earplugs in. Well, we were monitoring tower on a scanner (like we always do for these events so we know when someone is going to be parking on our ramp), and he responded promptly and you could hear him clearly while he was on the ground. As soon as he took off, the tower had to give him every call twice before he responded, then when he responded it was, "Say again, please." But, that was barely readable because you heard so much of his engine noise broadcast over the frequency too! It kind of scared me, to be honest.
