All I hear is how buggy Android 5.0 has been, I haven't upgraded my HTC ONE M7 yet and I don't think I will either.
Apart from Material Design (Love it btw) I'm afraid 5.0 will introduce bugs and slowdowns.
Hmm?
I haven't noticed any problems on my Moto X (2014). Wait, that's not true. Sometimes notifications at the top of the screen are not actionable.