I've had my N5 for about two months now, and I think I can give my impressions about this phone, since the first days excitement has gone. I'm coming from a HTC Desire HD, which I liked in some aspects, and hated in (many) others.
The phone seems well built, even if it is more fragile than my previous one, which I dropped several times without any fears of breaking it.
The N5 is a big phone, and it's not easy to use with one hand, but the screen is big, and nearly all the front surface is taken by the screen itself, so there's nothing to complain. Thanks to its slightly rounded back it is easy to hold, though the white version (which I chose) is much more slippery than the black one.
The screen is just awesome: its color reproduction is one of the best I've ever seen, and its brightness lets you read even under direct sunlight; the only drawback is about the viewing angles, which aren't bad, but could be better. Another minor issue is the auto brightness calibration: the display is always too bright indoors. While waiting for an official fix by Google, I discovered a flashable .zip file containing a more conservative brightness profile, which is perfect IMHO.
The touchscreen is very sensitive, too: it outperforms many Android phones, feels even better than the iPhone 5's and equal to the iPhone 4 and 4s' one.
Everybody is complaining about the camera, but I find that N5's shots are good enough to replace a point & shoot camera in most situations. I was surprised by their level of detail in low light condition: their definition was extremely good, and the OIS helped a lot. However, I can confirm that even after updating to 4.4.2, the phone doesn't always focus the right subject at the first try, though the time to focus has been significantly reduced.
The Nexus 5's speaker is not particularly loud, but after the latest software updates it's similar to the one of many others Android phones (not the HTC One, though

), and it sounds less tinny than the Desire HD's one. Being on the bottom side of the phone, you can perfectly hear it even when the device is on a soft surface.
Battery life is what I expected from a modern smartphone: I can easily get to the end of the day without needing to recharge. In particular, its standby power consumption is negligible (<1% per hour), and I can use the phone up to 4-5 hours before it runs out of charge. Thanks to the RGB notification LED and its customizability, I know which kind of notification you received without needing to turn the screen on, which helps you improving battery life.
I didn't mention the smoothness and the overall performance of the Nexus 5 in many daily tasks because I think there's no need to

Instead, I'd like to invite everyone who's using Android 4.4 to try enabling ART: this new runtime really makes the UI snappier and smoother, at a cost of few megabytes of RAM and drive space, and I think it's the most important innovation of the latest major Android release.
Overall, this phone is amazing: I usually can point out the main flaws of a product after some usage, but in this case it's really hard to tell one. The worst aspects of the Nexus 5 (battery, camera and speaker) are decent, and everything else is better than average. I would recommend this phone to anyone, especially to those who want to leave the Apple ecosystem and give Android a try: Google's operating system has never been so intuitive and easy to learn, and this is the perfect phone to start with.