Like many here, I bought myself some QC25s not long after they came out, in May last year when I went to Europe. Simply awesome Noise Cancelling Headphones.
Then one of the cans stopped working back on January 30. I took it into Bose, and they replaced them on the spot no questions asked, and I got a receipt with a new 12 months of warranty.
Fast forward to the release of the QC35s with Bluetooth wireless and noise cancelling. I heard that they were trading them in in certain scenarios. I figured what the hell, might as well go and ask. So I took in the box and receipt and everything and asked if they would do a trade. Again, it couldn't have been easier, the girls was very friendly and helpful. It cost me $120 to upgrade. I can't recommend Bose highly enough (but I guess that's what you pay for, much like Apple).
If you have QC25's and want the new ones, I reckon it's worth asking particularly if you bought them from Bose.