I've been flying with my UFlyMike and Bose QC2 combo for a few months now. Overall I am very happy. They aren't much quieter than my previous Telex ANR 500. The biggest difference is weight. The Telex was heavier. Also the Telex used the odd ball 9 volt battery while the Bose QC2 uses a more common AA.
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Battery life has been very good. It helps that I fly a fairly quiet plane. I get about 50 hours of use with name brand batteries.
I've gotten used to having the FAA TSO required headphones under the Bose QC2. The Captain's I fly with all give me a double take thinking I have a MP3 player and my headset. Once I explain it they either get it or think it's too much trouble.
Once I'm up at cruise I take off the headphones and use just the QC2s. My company manual only requires headphones and booms mikes below FL180.
Another perk is being able to change out the microphone for the stock cable during deadheads and enjoying regular music.
Would I buy it again? Yes. The Telex 500 ANR can be had for about $450-$510. A Bose + UflyMike setup cost a little over $600. Being able to use AA batteries is a huge plus in my book.
Bose doesn't sell QC2's anymore. The QC15's I also own sounded a little off when I first used them. Could have been my headset, not sure. UFlyMike has great support and mentioned no issues when using the QC15s. For those who require a TSO'd headset, to my knowledge the QC15 isn't TSO'd yet.