The Nexus 5 is the latest Android phone to be endorsed by Google (and manufactured by LG). It’s getting good reviews and the price is good for the specs. I just bought one for my wife, I got her the 32G version because when I bought her a Nexus 4 at the start of the year  I chose the 8G version and regretted it ever since. The size of apps is always increasing (some Android games need more than 1G of storage) and higher resolution screens drives the use of high resolution video.
Above I have pictures of the Nexus 4, the Nexus 5, and the Samsung Galaxy Note 2. The photo of the phone backs captures part of the sparkling pattern on the back of the Nexus 4 and it looks much better in real life (IMHO) because it shimmers as you move the phone. The Nexus 4 looks so good that there’s even a transparent case specifically designed to show off the rear panel . It doesn’t seem likely that anyone will design such a transparent case for the Nexus 5, it’s a good phone to cover up IMHO.
The Note 2 isn’t the most attractive phone, but I think it has a streamlined elegance of being optimised for it’s function. The Nexus 5 has it’s camera sticking out, it would be better if they had just made the entire phone thicker and given it a bigger battery but for people who don’t want good battery life I guess it’s a way of providing a better focal length without making the phone thicker. Sticking the IMEI number on the back of the phone will be useful on rare occasions (and might be a security issue on more occasions) but it definitely makes the phone less attractive.
The quality of the Full HD (1920*1080) display is obvious. The text is slightly clearer when viewing maps and the graphics in Ingress look nicer. Before I used the Nexus 5 I didn’t think that there would be any benefit in having such a high resolution in a phone but now I realise that I was wrong. The higher resolution is clearly better.
Chris Chavez wrote an article for Phandroid about a rumored Samsung phone with a 2560*1440 display . If such a device had a 6.6″ display (IE a new version of the Galaxy Mega) then it would have the same dot-pitch as the Nexus 5. If such a device had a 5.5″ display (like the Galaxy Note 3) then it would have a 15% greater DPI than the Nexus 5.
It seems that a higher DPI provides a real benefit and this is probably the biggest reason to choose the Nexus 5 over the Nexus 4 and most other Android devices.
Comparing with the Nexus 4
The Nexus 5 has the same amount of RAM (2G), a slightly larger display (4.95″ vs 4.7″), higher resolution (a big deal), faster CPU and GPU, and optical zoom. Faster CPU isn’t usually going to be a big deal (apart from the fact that more CPU power is needed as well as more GPU power to drive the higher resolution display).
The Nexus 5 can come with 16G or 32G of storage while the Nexus 4 has options of 8G and 16G. If you want more than 16G of storage then that’s a real benefit for the Nexus 5, but if you only need 16G then it’s not an issue.
It seems that when playing Ingress on a Nexus 5 it’s more likely that running another program (such as Google Hangouts) will cause Ingress to be reloaded than it does on a Nexus 4 or a Galaxy Note 2. While I haven’t done a good comparison of the Nexus 4 and the Nexus 5 in this regard I’ve compared the Galaxy Note 2 and the Nexus 5 well. My Galaxy Note 2 (which has many daemons running) is much less likely to cause a reload of Ingress (IE have run low on memory and terminated Ingress) than the Nexus 5 my wife is using (which has very little running). So it seems that the OS build on the Nexus 5 uses more memory than the Galaxy Note 2.
The Nexus 5 has Gorilla Glass 3 vs Gorilla Glass 2 on the Nexus 4. As my older Android phones with Gorilla Glass 1 (Galaxy S and Sony Ericsson Xperia X10i) didn’t get any scratches that matter I don’t think this is a benefit for me. Maybe if I lived near a beach I’d care more about this.
I think that the most significant benefit of the Nexus 5 over the Nexus 4 is the higher resolution display. The optical zoom should provide a theoretical benefit when taking photos, whether that results in better pictures in practice would probably depend on how you hold your phone, the available light, and other factors.
I think that if it was possible to buy a Nexus 4 at a sensible price (IE something less than the $250 that Google last charged) then for most people the Nexus 4 would be a better choice than the Nexus 5. But as ebay is full of Nexus 4 phones selling for a higher prices than the Nexus 5 it seems that buying a Nexus 5 is the only option. The range of phones that Kogan sells  doesn’t have anything for the same price that compares on features.
The heat produced by the Nexus 5 is significant and noticable. After some light Ingress playing on a cold day my Galaxy Note 2 with a gel case (that keeps it warm) reported itself as having a battery temperature of 34C. My wife’s Nexus 5 reported a temperature of 43C. While the thermometer in the phone might not be the most accurate I don’t think there was an accuracy problem, holding my wife’s phone was unpleasant and felt like it could burn my hand if I held it tight (40C is the minimum temperature for burns).
It seems that a Nexus 5 isn’t a good choice if you want to play Ingress in a warm part of the world (EG most of Australia in summer). Also heat dissipated is directly proportional to power use which is going to be a problem for a phone that doesn’t permit replacing it’s battery.
I’m quite disappointed with the Nexus 5. I expected it to be at least as good as the Nexus 4 in every way and better in many ways. Instead it’s not always as good as the Nexus 4 and the ways that it is better won’t necessarily provide benefits for everyone.
The heat and power use problems are really going to hurt the use of it. But I guess we can always hope that Google release a new Android build that reduces the power use, they might even have a new build that uses less RAM too.
I would not consider getting a Nexus 5 for my own use. For my use the Note 2 is clearly more suitable, the larger screen more than compensates for the clarity that the Nexus 5 gets from it’s high resolution display. Also I REALLY like having a hardware home button. I’ll probably get a Note 3 when the price drops, I’m not interested in paying $649 for a phone and I’m also not interested in replacing a phone that’s less than a year old. So maybe I’ll get a Note 3 in the second half of next year.