Well, I miss that a little, obviously, but since I was running the 15 inch in 1440x900 mode I am losing only a bit of that with the default resolution setup on the 12 inch (although I can make the rMB look like 1440x900, but then everything looks pretty small).
Perhaps the only downside of this laptop has to do with the underpowered CPU. I noticed a really funny situation last evening: while I was watching snooker on Chrome on the BBC player (Safari requires flash which I don't install and that's why I use Chrome in some situations) I decided to make a FaceTime call. And I can say that even after closing some other apps running in the background, Chrome and FaceTime were hogging the m5 CPU so much, that literally each app was freezing every other second in turns

Moving on a different workspace to open Finder and do some simple stuff was ok, but I think the graphics side was severely impacted when the video from BBC and the one from FaceTime were sitting on the same workspace side by side.
And speaking of browsers, Safari does a pretty good job with 15-20 tabs open, although I noticed that sometimes CMD+T takes like a second to open a new tab, which is annoying.