I recently buy an all new iphone 5s. Yes it is thee year old product but still a good deal.
The best thing about apple is gives you up to date update to their all products so you will not feel that you are using a three year old phone.
If any one ask me is iphone 5s is a good deal in 2016 than definitely my answer is yes it is. I m up to date of ios 9.3.2 butt I never feel slow or laggr responce from my iphone. So yes it is good deal and must buy product if you want to switch on to the ios.