In response to OP: kind of.
Because I like things clean and reliable. Whenever I've bought or extensively used other phones (Samsung & Sony), I always ended up eventually becoming too frustrated with things not working, or the OS just being too ill designed.
With that said though, to me the N5 was the last really solid Nexus in terms of design and hardware. N6 felt too cheap in my hand and those that have come after are just...weird. The Motos still look great though, and I guess they could be included in the 'Nexus' category.
For now I'm allowing myself to become fully submerged in an all-Apple set up, AW, iPhone, new Mac etc, and at the moment I'm very happy with these. But, I'm never the one to say 'never', so who knows... And if something would lure me away, it would probably be a really nice new Nexus or Moto.
I know I'll start drooling next fall when the new Note comes out, that can't be helped, and my fingers will end up fondling the credit card while walking around the Samsung mini-stores... But sadly my bad experiences with Samsung are so extensive that I'll probably end up listening to the voice of reason.
So I do have a feeling that if really cool things start happening over in the Android camp, and my urge for change fires up again, and whomever designs the next Nexus really runs a tight ship - a Nexus is the only thing I'd leave my iPhone for.