My take on the Lumia 920 vs the Nexus 4 (having owned both)
I will try to keep this as unbiased as possible
First some background on myself; I am a gadget lover to the extreme. I owned a T-Mobile G1 on launch and used it for two years (I would have gotten a new phone sooner if I could have because of the bugginess). After that I switched to VZW and got a Droid X which lasted for a year. The DX became way too buggy to use, so I payed full price for an iPhone 4s, which served me until this past month, when I received both the 920 and the nexus 4. So here we are. I have spent two weeks using each phone and I am prepared to make observations about both. Take from this what you will.
* The hardware feels second to none. The screen is absolutely gorgeous, and the phone feels indestructible in my hand.
* The OS looks beautiful. It is incredibly smooth, and the UI consistency (even in 3rd party apps) is refreshing. The UI consistency is easily above apple and IOS.
* Keyboard is extremely well done. Key presses register correctly and it feels right. On par with the IOS keyboard. Wordflow is super handy, and is much more accurate than similar prediction methods i've seen on android.
* Battery life is amazing. I know a lot of people have had issues with battery life, fortunately i was not one of them. I can easily get through a full day with 50% battery left.
* Lets talk about the elephant in the room: Apps. Part of the issue here is that its tough to differentiate WP7 apps from WP8 apps. The WP8 apps feel great; fast, responsive, stable. Baconit (Which was recently updated) is an amazingly well done WP8 app. Sadly, most apps I've encountered have not been updated. Rdio for example, which has been my de facto streaming app on other platforms, hasn't been updated since August, and is super buggy at best, but mostly un-usable.
* Continuing on Apps: The other side of the app issue is the lack of apps altogether, various staples on other platforms are missing from WP8 entirely. I know a lot of them are coming soon(TM), but in the mean-time we're left waiting.
* A caveat on the battery life performance: I had a realization while I was using this phone that part of the reason I was getting great battery life was that I wasn't using it as much. There were no "killer apps" that had me constantly glued to the screen (Well except Baconit) and I found myself using the device mostly as a phone.
* Windows App Store: needs some work. Im sure there are good apps out there, but using the WP8 store to discover them is difficult.
* Music: since Rdio wasn't really an option, I signed up for Xbox Music pass (background note: i previously owned a zune HD with zune pass). The app itself is great, though i dont like how the store feels separate. Playback and the UI are amazing, and i really appreciated Nokia's additions of an eq and Dolby Headphone. The one thing that irked me (coming from Rdio), is that in order to have an album appear in my collection, I had to download it. Rdio lets you pin music to your collection, so you can browse your whole collection even if it isn't on your device. Xbox music allows you to do this, apparently, only if you purchased the song/album. Any music can be streamed directly from the store, but it is much more cumbersome. Now I dont sync music from my comp to my phone, so I can't comment on that.
* Unified messaging is easily this phones killer feature. Im an avid user of FB messaging, so being able to look in one place for both texts and fb messaged was a godsend. No app on any other platform compares to this, which is really a disappointment (ill talk more about this in the android section
* Wireless charging is very handy, and has become by normal way of charging my phone
* Ordering this thing was a nightmare and a half. They were sold out on the day of release, then when they opened orders up again two weeks later, it wasn't much better, though i was able to get my order through. Then of course it took two weeks after that to actually get my phone
* The hardware feels very high quality, but also very fragile. The glass back with the "digital dots" looks amazing, but i am forever in fear of it breaking.
* The screen is... ok. My phone has two backlight bleeds at the top, which are a bit annoying (but not enough to justify trying to go through the nightmare return process). Also, I can notice the lower DPI of the screen unfortunately.
* Android really improved its smoothness and stability since I last used it. The Butter project really feels like its namesake, and during my use, I didn't notice any crashes (both app and OS).
* No facebook contact integration was disappointing. I had to hunt down a 3rd party app that kinda-sorta integrated it, but it isn't perfect.
* Coming from windows phone, I really yearned for a universal messaging app, and was disappointed to find none. I know FB is working on making its app capable of sending texts. Considering the openness of android, im really disappointed that no one has made such an app yet.
* Android's UI is.. meh. Don't get me wrong, Holo is much better than the older stuff, but it still feels dated. Plus the fact that only a handful of apps follow the Holo guidelines. Its a hodge-podge.
* Google Now is super-powerful and awesome. Unlike siri (and to a lesser extent Bing search), i found myself using it constantly.
* Navigation is second to none, though this can basically go without saying.
* I was having numerous data connection issues both wifi and HSPA+. I'm not sure what the root cause was, but it was pretty disappointing.
* Since I was back on android, I switched back to Rdio... only to be disappointed again. The app was super-slow, often showing the loading circle for minutes while trying to browse my collection. While this may be attributed to data issues, it was also happening while trying to browse offline content as well.
* Android's stock keyboard has come a long way since the G1 days, and while it's not perfect, it is significantly improved. the swype-esque functionality I found particularly useful.
* For some reason, even though they both supposedly support the same charging standard, my Nexus 4 wouldn't pair with my nokia wireless charger.
I think that about covers it. If you have any questions and/or want me to talk about something i didn't cover, let me know