I have the base rMB 2015. Came from MBP 15, 2012 and rMB did feel more laggy but portability was worth it. I guess the keyboard is ok even though i do make writing errors. I use the LG UltraFine 4k Monitor with the rMB and even though it works, it gets a bit laggy with 4 different writing programs opened up at same time. Does your 2017 work smooth with the 4k screen? Wondering if I should upgrade and what would be best configuration. I also do some 4k FCPX edits on this MacBook. It works fine but not as great when running on the 4k screen. I guess I'm really pushing it. Wondering if the 2017 model would solve these issues.