I used and loved the QC2/UFM for several years before I knew just how dangerous it was (thankfully Jeff and Chuck saved me from grievous harm by banning their use!).
I then came to my senses, and bought a $500 Sennheiser HMEC-46, which was a POS in just about every way possible. Little to no noise attenuation, uncomfortable for more than 30 minutes and it died after about 2 years of use. The only good things I can say about that POS is that the battery life was excellent (LEDs don't draw much current, and apparently, the LED was the only thing powered when it was on), and I was able to write the $500 off of my taxes.
I used the company issued Telex for a while, which offers BETTER NA than the HMEC-46 (which isn't saying much), but the audio fidelity was so bad that I had a hard time understanding controllers, especially females. Also, the mic is really noisy on the intercom when using the hot mic, but you won't notice it unless you have a real NA headset. The HISSSSSSSSSSSSSSSS gets old when the FO has hot mic latched on. The only upside to this thing is that it was free, and is small/lightweight. I never broke mine, but it seems pretty delicate.
I finally relented and bought an A-20, and it is the best headset I've ever used. It's definitely heavier and bulkier than the QC2/15 setup, but the attenuation is better (maybe a little TOO good). I find it just as comfortable as the QC2/15 on long legs. The only downside compared to the UFM setup is size and weight. Battery life (2AAs compared with 1 AAA for the QC2) is pretty good. I get about 2.5 4 day trips out of a set as long as I remember to use the auto off feature.
The QC2/15 setup, as allowed to be used by SW, is a bit of a PITA now. First, you have to send the thing to UFM to be TSOed (a requirement unique to the UFM setup), which consists of Mike putting a few stickers on the thing. Then, to satisfy the TSO, you need to use specific earbuds UNDER the QC2/15, which plug into the AUX port on the UFM. Without meeting these requirements, you can't use them in a SW cockpit. The reason for all this TSO BS is that the QC-2/15 won't pass audio signal with a dead battery, and FLT Ops was deathly afraid that someone would ignore the HOURS of degraded audio flashing power light and incessant clicking when the battery gets low, and miss a radio call. The other reason is that the UFM has an AUX input on it, and you know, someone might be tempted to plug an ipod into it while flying, which would immediately result in a horrific crash, of course. Also, I think someone's relative at the GO works at Bose, and they didn't appreciate Mike cutting into their aviation headset business (they actually brought a lawsuit against him, which was dropped, ignoring the fact that many pilots bought QC2s that they wouldn't have bought otherwise, but I digress).
Overall, the QC2/15 with the UFM is a GREAT solution to the noise problem in a 737, but for our operation requiring the TSOed variant, I think the hassle factor is about a wash between the bulk of the A-20 and the friggin spaghetti wiring required to use the UFM/earbud combo in our cockpits. Just make sure you have a handful of AAA batteries when you go fly.
If you aren't saddled with the TSO nonsense, then the QC2/15 is the clear winner from a price, portability and hassle standpoint.
All IMHO of course.
Oh, and Wave, you can use the A-20 when riding in the back for both NA and music etc. You just have to disable the "auto off" feature that turns off the headset after a while when not plugged into the aircraft.