The vote is how I would expect on a forum such as this, but it's definitely not representative of normal non-techy people I know in person. I know a couple of people who have upgraded to it from a 4, 4S and 5. The small screen is real winner with lots of people who just want a compact, speedy, functional iOS phone, but with a decent camera.
It's definitely not only selling well in low end markets. It's been limited stock around me in London since launch. Although I'm sure the the lower price does help, even in Western markets. It's a decent saving over a 6S.
I think it's great they decided not to gimp the internals and instead keep at as close on a par as possible to the 6S in a smaller package. I have a feeling Apple didn't anticipate how well it would sell seeing how low stock is in most major metropolitan Cities in the US, UK and some other markets.
Like Chris said, it's down to your personal needs. Get whatever suits you, all 3 are really great choices for different people. It's the best phone lineup Apple has ever had.