I'm quite impressed by the quality of the sound through the supplied headphones. Granted, they aren't studio monitors or $300 Sennheiser's, but if you run the app to tune the sound to your ears, they are pretty good. I haven't tried them at full volume, but just to the limit where Android gives you the pop up about loud music. All in all, 4/5.
---------- Post added at 01:32 PM ---------- Previous post was at 01:18 PM ----------
I've only had my U Ultra for just over a day, and I'm quite impressed with it. This isn't my first HTC (first was the Amaze 4G), and aside from the disappointing m8 that I had, HTC keeps making underrated flagships. I'm surprised how little fanfare this phone has gotten, despite having the best camera I've used in a smartphone (even using an iPhone 6S for a time). When Oreo does come to us, then this should be an even better phone!