[Nexus 4 General] nawoa:
In my opinion onscreen buttons are an incredibly good idea:

- Makes the active parts of the device more centered, which looks nicer IMHO

- Allows for a smaller top/bottom bezel

- Allows the device to be completely smooth and uniform from the front, noticeably distinguishing Android devices from iOS or WP devices

- Both the top and bottom bezel can be held comfortably without accidentally hitting any buttons

- The onscreen buttons can go low profile automatically when apps request this or hide entirely to allow for full-screen video, unlike regular buttons which stay there all the time and even light up when it's dark, which can be distracting when trying to watch video

- Provides full widescreen when it's important (video) but otherwise "moves" the display upward a bit to make it more comfortable to use one-handed

- The closer a screen is to having a 1:1 aspect ratio, the larger it will be; ie, a 5" 16:9 display has fewer square inches of screen than a 5" 16:10 screen; do the math, it's true... so if someone says the 4.7" Nexus 4 display is closer to a 4.5" display with the navbar included, it's actually still larger than a 4.5" 16:9 screen (I'm adding some numbers at the bottom of the post to demonstrate this)

- Allows for future software updates to change buttons without making devices obsolete or troublesome to use, like all HTC phones for example

- When you're swiping down on the display, you can swipe right over the onscreen buttons and Android knows you're doing a gesture, not trying to use one of the buttons

- Allows the selective elimination of the obsolete "menu" button, which was IMHO one of Android's greatest weaknesses in usability because you never knew what exactly the menu button would do (if anything)

- ROMs can tweak what buttons appear and how, which is a nice added layer of customization

They do come with a compromise in gaming though, since it's easy to misjudge where the "screen" ends and accidentally hit one of the buttons. With a custom ROM you can hide them using the power menu, but I don't think "use a custom ROM" should ever be the only solution to a problem. It's very silly to suggest ordinary people should go to such lengths to address legitimate OS issues. ROMs should ideally be for customization or adding "bonus" features, not for correcting significant problems.

I think Google will implement some kind of button hiding system in the future though. I don't know whether they'll use a button combination, a power menu option, or a gesture, but I'm pretty confident they're not blind to the issue and would like to address it. A gesture would probably be out of the question since it might conflict with gestures that app developers are already using, and adding even more functions to the power button would probably just be confusing (not to mention a rather slow method), so maybe something like pressing volume up+down simultaneously would work well.

In any case I think onscreen buttons are a great (if imperfect) solution to the problem of OS navigation. They're uniquely Android as well, which I very much prefer to mimicking another platform's solutions.

Nexus 4 (15:9) vs Galaxy Nexus (16:9):

N4 w/ navbar: 4.70", 1280x768, 1.667:1 AR = 4.03" x 2.42" = 9.74 square inches

GN w/ navbar: 4.65", 1280x720, 1.778:1 AR = 4.05" x 2.28" = 9.24 square inches

N4 w/o navbar: 4.44", 1184x768, 1.542:1 AR = 3.73" x 2.42" = 9.00 square inches

GN w/o navbar: 4.38", 1184x720, 1.644:1 AR = 3.74" x 2.28" = 8.52 square inches

Nexus 4 with navbar is only 0.24" smaller than Galaxy Nexus without navbar: 9.00 square inches vs 9.24 square inches

Nexus 4 vs "equivalent-sized" 16:9 devices:

N4 w/ navbar: 4.70", 1280x768, 1.667:1 AR = 4.03" x 2.42" = 9.74 square inches

4.7" device: 4.70", 1280x720, 1.778:1 AR = 4.10" x 2.30" = 9.44 square inches

N4 w/o navbar: 4.44", 1184x768, 1.542:1 AR = 3.73" x 2.42" = 9.00 square inches

4.44" device: 4.44", 1280x720, 1.778:1 AR = 3.87" x 2.18" = 8.42 square inches

Nexus 4 w/o navbar (4.44") is equivalent in screen space to a 4.59" 16:9 device with no navbar:

N4 w/o navbar: 4.44", 1184x768, 1.542:1 AR = 3.73" x 2.42" = 9.00 square inches

4.59" device: 4.59", 1280x720, 1778:1 AR = 4.00" x 2.25" = 9.00 square inches

Galaxy Nexus vs "equivalent-sized" 16:9 devices:

GN w/ navbar: 4.65", 1280x720, 1.778:1 AR = 4.05" x 2.28" = 9.24 square inches

4.65" device: 4.65", 1280x720, 1.778:1 AR = 4.05" x 2.28" = 9.24 square inches

GN w/o navbar: 4.38", 1184x720, 1.644:1 AR = 3.74" x 2.28" = 8.52 square inches

4.38" device: 4.38", 1280x720, 1.778:1 AR = 3.82" x 2.15" = 8.20 square inches

Galaxy Nexus w/o navbar (4.38") is equivalent in screen space to a 4.465" 16:9 device with no navbar:

GN w/o navbar: 4.38", 1184x720, 1.644:1 AR = 3.74" x 2.28" = 8.52 square inches

4.465" device: 4.465", 1280x720, 1.778:1 AR = 3.89" x 2.19" = 8.52 square inches

Some interesting iOS device comparisons:

iPhone 4: 3.5", 960x640, 1.5:1 AR = 2.92" x 1.95" = 5.65 square inches

iPhone 5: 4.0", 1136x640, 1.778:1 AR = 3.46" x 1.95" = 6.84 square inches

N4 w/ navbar: 4.70", 1280x768, 1.667:1 AR = 4.03" x 2.42" = 9.74 square inches

N4 w/o navbar: 4.44", 1184x768, 1.542:1 AR = 3.73" x 2.42" = 9.00 square inches

GN w/ navbar: 4.65", 1280x720, 1.778:1 AR = 4.05" x 2.28" = 9.24 square inches

GN w/o navbar: 4.38", 1184x720, 1.644:1 AR = 3.74" x 2.28" = 8.52 square inches

Of particular note, take a look at the screen widths:

iPhone (all): 1.95"

GN (4.65"): 2.28"

N4 (4.70"): 2.42"

This explains why despite the much larger screens Android devices tend to have, typing on an iPhone isn't that much different.

There's a similar phenomenon with Android tablets (10.1") versus iPads (9.7"):

iPad (4:3): 7.76" x 5.83" = 45.17 square inches

Android (16:9): 8.8" x 4.95" = 43.59 square inches

Android (16:10): 8.56" x 5.35" = 45.85 square inches

Notice that the Android tablets are between 1.04" and 0.8" wider and between 0.88" and 0.48" shorter. This, in addition to typically being heavier, makes them much more awkward to hold.

On the other hand, the story looks pretty bleak for the iPad's 4:3 screen if you're talking about media consumption: the iPad will display 16:9 video with 33.82 square inches of screen space, while a 16:10 Android tablet will display the same video with 41.21 square inches of screen space.

I made all these calculations using a tool I found online.

Finally, and perhaps most importantly for everyone reading this: notice how I've written this huge informative post full of proofread original content in real English and my signature doesn't take up an entire page? And how I'm not begging for "thanks" like some kind of Reddit karma whore? And how I don't have any obnoxious bull**** at the end of my post about what I'm using to type this message? That's because I'm not an asshole. Hint, hint.