Used the phone for a few days now:
The build quality is very good, but not excellent. If I pinch the lower left corner of the phone a bit, I can hear squeaking sounds. It's not that huge and the rest of the phone feels solid and very good in hand, but it's noticeable if you pick up your phone from your pocket using that corner and that gesture. It's been noted by other owners below that their units didn't do that, and mine doesn't always do it either, but the possibility of it is worth noting. The curved glass at the edge of the screen is really pleasing, as well as the rubbery edge. Having the power button on the right edge takes time getting used to if you come from a phone with a different layout. I used to have the sound rocker here, so you can guess at my somewhat repetitive mistakes. It is a nice phone overall, a bit bland (I mean, it's a slab of black glass, what do you expect?) at a glance, but really nice upon closer inspection, as hinted by that holographic back cover which I find mesmerizing (I don't need much, do I?).
The camera is a phone's camera (duh), in my opinion it is sub-par but I come from a place where shooting stuff I want to look pretty is done with nothing less than a DSLR, so there's that. If you want me to go into more details, I'd say the auto-focus is relatively slow, macros are nearly impossible, colors are a bit washed out but easily editable, and depth of field is too deep for me. Portraiture is not going to be this phone's strong suit. The photo editing software embedded in the gallery app is, however, really good and pleasing to use. Finally, Photosphere is a nice addition but it is also a real gadget. I found it great when I wished to capture the view from my hotel room, but I found it way too time-consuming when I tried to sphere the actual hotel room.
Performance has been fantastic so far, I've never seen a lag in any game I've played (Sword and Sorcery, Dead Space, Canabalt, Swing Shot, S&S, Draw Something...) and not even using Chrome. My Wifi and 3G+ reception has been good, and so was the call reception.
Battery life is standard for android flagship devices. I can get a day of medium use, with auto-brightness, wifi and 3G on all the time, some gaming, medium to heavy internet browsing, few texts and emails. On Saturday I unplugged it at 8am, wired it back at 11.30pm and it had 2% left with 5 hours screen time, heavy internet browsing, some games and quite a considerable amount of time trying to reach an antenna since I had spent the evening lost in the middle of nowhere in Normandy. My opinion on that is that it's still poor no matter what, but it's comparatively good when taking into account the industry's standards.
Android 4.2 is a joy to use, but that part has been covered a lot in the reviews. The quick notification toggles are great, the design choices are all working for me (that clock app is in my opinion better-looking than iOS's. I own both) and the smoothness of it all is striking. I have found the "People" app fairly well designed, but it lacks the option of displaying only people with phone numbers, something you get when reaching your contacts through the "Phone" app. That's a bit weird for me, coming from and Xperia device. Google now, though not a part of 4.2, is a really nice tool and does make the experience feel a bit more premium. Ultimately though, it remains clear that Google develops these products for the USA first, then tries to see how it goes when available globally. Trying to add a French football team (even the National one) to your sporting interests isn't an option (and I don't feel too bad about it). I'm pretty sure it wouldn't be able to track my parcels either.
The enhanced lock screen with widgets is more of a gimmick to me right now. Yes, in theory it is nice to have the ability to reach your mails without doing a full unlock, but I rarely have to check my emails unless I get a new one. And when that happens, I can just as well slide down the notification panel and click on the incoming email: it takes as many swipes, and it is as functional. However, there will be more widgets added as developers get to it, and it will certainly prove useful to some.
In conclusion, the Nexus 4 is certainly a very good phone, and certainly the best Android phone you can get on the European market now. I would gladly trade the cheap plastic feel and bloated software of a Galaxy SIII against this mild squeaking sound any day. The lack of LTE isn't an issue at all if you are not in the USA, and every other aspect of the phone fits at least this guy's need for a smart device. It is not perfect, and some will find gripe with the "only good" screen that should be "amazing", or with the camera that's "serviceable and good enough" rather than "terrific and soul-capturing". My only real concern remains battery life, and I can't fathom how a flagship device can maintain this laissez-faire approach to piss poor efficiency. Granted, this is very subjective and I expect this part of my opinion to change when wireless charging makes it virtually impossible for me to drain the battery down, and such as been my issue with all smartphones anyway. Additionally, this phone has been sold for 100€ less than the cheapest deal available for its closest contender in Europe (GS3). I expect the deal to be even more appealing in the US, and that alone makes the Nexus 4 a remarkable device: this is not just a piece of hardware, it's a cheap albeit premium piece of hardware. Keep it in mind these next 3 weeks.
Edit: Here are some sample pics taken with the phone.
The first two pics were not edited through the gallery software.