Yeah, I have a base 2015 rMB and I just don't see the issues you guys see. I have a little lag in Photoshop on really heavy projects and on QuarkXpress, but if I had to use it primarily I could. I never see beach balls. I edit on FCP all the time with it and other than exporting, it's as fast as my mid-2012 rMBP. For its specs, the rMB is a beast. And it's so portable.
I've debated getting one maxed out as my next computer, but I'm not in a rush so I'm waiting on the new pros. The biggest thing I want is a bigger hard drive. A little more power would be nice too. I feel like the m7 would probably be plenty for me, but if I'm spending that kind of money, it's tough not to go with a pro.