Sooo I'm finally posting my impressions of the Z3 Compact!..
Build quality is premium and it's a great looking phone. It's relatively thin (8.6 mm) with something I love: small bezels!
It is much smaller than phones the world got used to, but not that small. I have big hands and still can't access hamburger menus with just one hand unless I slide it towards the middle of the phone. Still, not sure I'm willing to go any smaller than this. Holding any bigger phone now feels awkward at first.
The USB port cover flap is prone to break if handled improperly. Also, it makes using the phone while charging a bit odd. Makes me wish one of those new waterproof USB ports. Waterproof certification was never a must-have for me, but it's handy - no need to worry about the rain, for example. It can even take a bath if necessary.
Screen is crisp and vivid. One thing I really like about the 930's screen is how good the colors look without being over-saturated, and the same goes for this one. Viewing angles are satisfactory. Since it's a LCD display, no risk of burn-in is a plus for me.
Although the camera has the same amount of pixels as the 930, it's easily surpassed by the Lumia. Decent, but simply not as good. It's great to have a dedicated camera button, so +1 for Sony.
It has a bigger battery than my 930, which is bigger and thicker. Lasts a day of heavy use: WhatsApp, Messenger, social media, browsing, music, etc. Light use on the 930 would drop the battery at a ridiculous rate, like 2-3% every 90 seconds or so - screen-on time must feel 3x better. Keeping Stamina mode on the whole time makes it last 2 days of moderate use.
Sound quality is very important for me. I listen to music on a daily basis on headphones and sound quality must be the best possible. Luckily, this phone didn't disappoint me on that department: loud and clear sound.
Running Android 6.0.1, resuming apps is usually very quick. Good use of resources, kind of puts my 930 (which has similar specs) to shame. Performance is one of the mains reasons I decided to keep the Z3C, I can't live without it anymore.
It packs a lot of bloatware, which I hate. Only some can be uninstalled, others can just be deactivated and hidden. Maybe I will root it to get rid of them once warranty expires. +1 for W10M, where you find few pre-installed apps and can uninstall what you don't want.
Having a notification led is cool. On the other hand, Android feels clumsy for some tasks - the data monitor is located in the settings menu and, without WP ability to pin anything to the start screen, you either access it there evertime you need it or use 3rd party apps (plenty to choose from, which is good). The action and notification center is better by miles on W10M, hands down. Almost everything I do on it can be done better there, including customization. Blocking SMS is a frustrating experience, I really miss W10M built-in blocker.
About keyboards, until I last used W10M prediction still worked like &$%#! for any word longer than 4 letters. Haven't had any issue with Google Keyboard so far (it learns quickly, even swear workds lol) and there's 3rd party keyboards to download. I'm hoping MS will release their keyboard on Play Store, but with the same quality level as before. However I do miss how easy it's to change language input on W10M.
Gestures (something MS axed) are available: answering calls by just picking it up and holding it next to the ear is a nice gimmick.
About apps... Obviously they are all there. I didn't found Microsoft apps all that better as people say. Weather for example, lag behing compared to its W10M version. MSN News crashed a lot on my 930 since day 1 and that always annoyed me, but it isn't perfect on Android - just more stable. Live tiles make a great difference on these 2 apps. On their case, widgets just doesn't do the justice (I'm yet to find a weather widget that is as good as Weather live tile). About Outlook, it doesn't offer more on Android for me and I have 0 complaints about it on W10M. Can't tell about Office - never really used it even on WP. Feels good to have such a better store experience, as even the Google Play app itself is better.
Google Maps can't save offline maps properly. Instead of selecting countries, states, etc to download, all it offers is drawing a rectangle over the region you want to download. Not cool. Luckily, Android still have Here Maps - offline maps work as usual there. Gotta love having options...
Bottom line: As much as enjoyed this phone, I still prefer using WP and would love to go back. Too bad the future doesn't look bright for it and it's dying more and more each day in my country (I simply don't see Lumias in the wild anymore). Still, this phone indeed lived up to my expectations, so I see myself staying on Android for the next years.