I don't have a 6.
I just can't get around the price. (The real price, and if you get it on a contract, you'll STILL pay that price. It just won't be as obvious.) You can get a top-of-the-line iPad for the same money. I think there's more value in the iPad.
Rather like looking at a three year old Range Rover to buy. Same price. Same condition. Same spec. Ones a FFRR and ones a SSRR.
Also, phones lead a harder life than other gadgets. When they end up underwater, dropped, or lost, cheaper is definitely better.

Re: other non-Apple phones. It's rather nice having the same apps and having already come to terms with iTunes. Can any of the others run iOS and play nicely with iTunes, etc?