I have had this device officially for a month, and so far it has been a great experience.
In the past I had a Motorola Atrix (it was good the first year, then it was very faulty, hardware wise), then I got a Samsung Galaxy S3 and I had it for a month until it was stolen from me (a great device, though TW is not my favorite interface), after that I got the Xperia Acro S which felt a bit as a step back in performance, but a step forward in durability, connectivity and UI. I used it for 2 years and after countless falls it survived without major damage.
Now I got the Z3 Compact after patiently waiting for a worthy successor to my Acro S, since the Z1 Compact did not convinced me with its camera, also I rather have a bigger screen on the same size of body. So the Z3 Compact actually ticked all the boxes I wanted for a new phone, and it keeps surprising me with certain features that I discover overtime.
The camera is not the best out there, but I enjoy it a lot, specially in low light situations where other phones simply give up. The High Sensitivity ISO mode works exceptionally well when you are in extremely low light situations and flash is not an option (far objects), and if you turn flash on, the mode will get even more light than what other hansets would. Slow motion video (Timeshift video) is very good and it is the most fun for me, though it will eat your storage really quick.
Also I enjoy the Multi Camera mode with my QX-100 and the videos turn out very interesting.
The digital stabilization works incredibly good, but it will make the field of view quite a bit narrower.
I love having a dedicated double-step camera shutter button.
I haven't dunked the phone in a pool but I did use it for taking pictures and videos on a pool without submerging it. I have rinsed it on the sink and I have taking showers with it. Wet finger tracking tech works ok, with occational touches caused by large drops of water on the screen, but the smaller ones get ignore.
The sound quality is actually very good, I keep ClearAudio+ on for my Plantronic BackBeat Go2, for my XSP-N1BT car stereo and for when I use the built-in speakers, however I turn ClearAudio+ off when using it with BOSE SoundDock 10, since it has too much bass, and also when watching movies with the built-in speakers, so I can hear voices better.
Stereo sound is there, and it works good when keeping the phone in front of your face, but the effect is lost if you place it further than say 30cm (12") away. The muffled sound can be improved with ClearAudio+ or with EQ depending on the music playing, and even if the speakers are not the loudest, they actually deliver decent bass!, something missing on most smartphone speakers (excluding HTC).
I love the Walkman app, I was a bit confused and undecided with the "home screen" on the app, but after using it for a while, it makes sense to show the content it does. I like the way it is also on Album but I dislike it on Movies. Back to Walkman, in my opinion it is the best music player included by a major manufacturer, it gives a lot of useful features (play queue, sense playlists, extensions, folders, music info download, song tag edits, etc) and at the same time it is very stylish, simply to use and sounds great. On the other hand, it lacks gapless playback and genre organization.
For phone calls only the lower speaker works when on speakerphone, and it sounds a bit tiny but it is a compromise made due to the feedback from the microphones. Using the earphone, the sound is actually very loud.
The screen is great specially for media consumption where X-Reality kicks in. The rest of the interface is a bit bluish but thats something you can get used to. Also the blue tone gives the illusion of being brighter than warmer tones. Movies and pictures look great on it and it does NOT need more resolution than what it offer. It is the perfect balance between ppi and battery efficience.
Speaking of battery, I constantly get over 5 hours of Screen On Time, when using my phone heavily (and I mean HEAVILY). browsing, navigation, gaming, music, bluetooth, and so on. Sometimes I get over 7 hours, and it has never died on me before the end of the day. I charged my previous device 2~3 times a day with my kind of usage, and I was lucky to get over 2:30 hours of Screen On Time.
I love this device and I hope I don't encounter the issues other people have mentioned. I have treated this phone very carefully but I have hit it accidentally a few times with hard objects without any consequence. I want this phone to give me at least 2 years of joy like the Acro S did.