Bought a 2017 MBP 15" 2.8 GHz i7, 256 GB SSD, 8 GB RAM.
I had a 2014 MBA 13" 4/256 until 2 years ago, and a 2016 MB 8/256 (M3) until this week.
My reason to upgrade is that because of a new job (self employed) I had to make more presentations with lots of pictures/photos, open technical drawings, etc. Before, I only used mail and office programs, so the processor of the MB didn't bother me too much. But now, with the new job, the MB was a real problem in terms of productivity.
So I chose to upgrade to a (much) larger screen and (much) more processing power.
I do have to say, that the MBP 15 is great. The extra screen real estate and the processing power obviously make an enormous difference. But the fact that this machine is literally two times larger and heavier does have its drawbacks. I really loved the portability of the MB, which had a great screen as well.
I am glad with the new machine, even though I didn't wait until June/July. I got the machine for a nicely reduced price, so decided not to wait for the 2018 version.