I would hold off buying a new machine right now - especially when the new Mac Pro isn't here yet (just as the Yeti isn't, and the monster of Loch Ness....)
I am on a MacBook Pro Retina as well (with 16 Gb RAM) and have not experienced stability issues in editing - my problem is with importing my older images into the catalog, where I get half-dead catalogs with all folders having lost their folder names. When I tried to create a catalog with 10 000 images, the whole system imploded - definitively a software issue.
I guess with such a new release, different people with different set-ups will stumble upon different problems.
How much RAM do you have on your machine? Your IQ 180 files are way larger than my 5D 3 files.