My GNex is still doing just fine! The recent 4.x dot releases have been a bit shabby, but fundamentally things work (bluetooth cough cough). I guess being stuck with a 4.3 device for testing will be ok. I do most of my Android dev and testing on the first gen Galaxy Tab 10.1 which is stuck on Android 4.0, and my consumption/games on a Nexus 10 which Google will no doubt abandon soon.

Doing dev and debug on a device I don't actually use has been effective. My most productive features have been having the device in a dock, and using wifi adb so I don't have to bother with cables.