I totally agree with you. I went down to the Apple store on Sunday and they had 6 of these out on display. Of course all of them were the 1.1ghz processor. But while playing with the laptop, I noticed lots of lag in the UI from using Safari, youtube, etc. I wonder if the 1.2 or 1.3 would be better but didn't have one to test. If this is the case, I may have to go with a MBP and wait a few years for them to resolve this.
I brought my 2015 MBPR into the apple store today to get a REAL world test comparison and size comparison. I 100% noticed a difference, and the UI was a little more choppy on the MBR. But that is a sort of a no brainer since my MBPR houses a 2.7ghz over the 1.1 core M. Now its not like OMG don't buy horrible but if you are used to a more powerful machine or this will be your main machine. Its food for thought.
I still prefer the screen size and footprint of my 2015 MBPR, but i do appreciate how thin and light the 2015 MBR is. But i don't travel, other than going from room to room in my house. My preference would be a 14" MBR in the footprint of a 13.3" MBPR but thinner etc. I think thats coming down the line.