Also a 2015 MBP user chiming in. I see absolutely no reason to upgrade. Currently in need of a battery replacement. Still deciding whether it's worth attempting myself or to just shell out the extra $100 for Apple to do it.
I'm surprised no one has mentioned the price of the laptop that the author gets. The thing is $1,400 base price - and that's with a 120 GB SSD and 4 GB of RAM. Up it to 8 GB of RAM and a 500 GB SSD and you're paying $1,7000.