I've had it for a while on a Nexus 4. Nothing that exciting. The photo sphere thing came in handy (only just noticed it recently, and assuming it was introduced with Kit Kat).
Photosphere was introduced in Jelly Bean, it was a launch feature of the Nexus 4.
Any of y'all gone into developer mode and enabled the ART runtime instead of Dalvik. It did wonders for my battery life on both Nexus 5 and Nexus 4.
could you clarify this? what does it do...
Dalvik runtime is a JIT runtime, compiling the program as you run it. ART runtime is precompiled (takes forever to compile upon first boot after changing the runtime, or after an OS update) but it's worth it for the savings in battery life, and the slight (but noticable) speed increase that occurs. There are some compatibility issues though, specifically with WhatsApp and some games. I've not come across any compatibility issues, since I don't use WhatsApp and rarely use my phone for games.
Definitely worth using, especially for the speed increase it gives when switching between apps.