The reason why an Android developer needs a Nexus 10 is simply because it is awesome and every developer wants the latest and greatest! Right?! Well, yes but there is also another really good reason you, as an Android developer should get one.
This is something that I didn’t even know about even though I have been in and around Android from the very beginning. I can credit Jerry Hildenbrand with Android Central to pointing this out. Using a couple of handy commands in adb you can effectively change the resolution and pixel density of your display. Due to the fact that the Nexus 10 has such a high resolution and pixel density you can effectively test nearly all resolution and pixel densities in existence with Android devices today.
To perform this simply turn off the screen of your device and run the adb commands which are:
adb shell am display-size *your display size*
adb shell am display-density *your pixel density*
Then when you turn your device on it will be emulating the values you passed it.
This is a very handy feature and really does allow you to buy one device and check your app or even responsive web designs against all the different sizes out there and really takes away a lot of the guess work.
For more information on these commands head over here.