I've had mine for over a week now but I've only been properly been using it since Saturday when I sold my S3, I am still for my new Diztronic case to arrive directly from them (nearly a week now) so in the meantime I'm having to use the phone with a phone sock and no protective screen :/
Anyway - I must say, this phone is amazing. It's noticeably quicker than my old S3 and it feels much nicer in the palm of my hand, and as the other member on here says - the speakers are LOUD! But they are excellent, the clarity and sound is near enough the same as my Altec Lansing speakers!
As other have also echo'd, the camera does indeed have some room for improvement as daylight shots can be very hit/miss at times but at the time same, low light/night photos are very good. Front camera - I've not had the chance to test it out yet. Hopefully as discussed the camera issues will be resolved with a future firmware release.
Screen & touch - nice, bright and the detail is excellent, however when it comes to colours & details I'm no expert but to me it looks better than the quality on the S3. The touchscreen however I must say is also smooth, responsive and typing to me feels way easier compared to my old S3. The front touch buttons are also good, but at this stage I cannot give a definite answer as I'm still getting used to the phone but for me sometimes I have to press the buttons twice before it does something (probably because my finger isn't positioned on them properly, knowing me!)
Battery - Wow, a massive improvement coming from my old S3! On the S3, a full charge would roughly only last for 18hrs at the most with how I generally use my phones at the moment (Facebook, Twitter, Internet, Messages and a bit of the camera). However, on my new One I have managed to get around 30.5hrs from the battery before I put it on charge an hour ago, and the phone is currently undergoing it's second full charge. I have practically been using my One for the same things as mentioned that I did on the S3 but overall so far I am amazed by how long the battery been lasting.
Build and overall quality of the phone. It's got to be said that one of the main reasons I've gone back to HTC this time is because how well built their phones are, and the general quality of them in the palm of my hand. The old S3 did feel well built but I was never blown away by the general plastic feel of the phone and, as all of you know will know the HTC has a Aluminium casing, which to me feels really comfortable in my hand and it makes the phone look and feel more premium. I know looks are not everything with a phone but to me, this is one thing to think about. I have also been reading reports on here & on XDA that some users who acquired there One's literally when they first became available a few weeks ago that some have been people experienced slight defects with the casing i.e. gaps between the casing and the screen/corners. However with mine, I'm glad that mine is totally free of any cosmetic defects
As I have only been using the phone properly for the past couple of days this is all I think of for now. Though here is a quick summery of slightly niggly things that I want to note about the phone (my opinion only of course):
Notification/battery/charge LED could be better positioned and when the phone is rested on a table, the LED can be hard to spot unless you're directly above the phone.
Volume keys - HTC could have put a bit more thought into this as sometimes they are hard to feel due to them being the same height as the rest of the casing (unlike other phones where the volume keys are slightly raised). If you're not directly looking where to put your thumb, the keys can be a bit of a challenge to find.
Liam