Let me add to this as well! I just purchased a rMB 3 days ago since my 15 inch rMBP needed to have its keyboard repaired (some loose keys which were horribly popping out). The reason I went for this is because I was curious about how well this little thing performs in real life and I have to say that I am absolutely astonished by how much this machine can do given it's specs and thinness (btw, I went for the m5 configuration I could buy from the store). Surely, running many apps at the same time won't result in a very smooth experience, but this machine has already exceeded my expectations anyways.
And really, after just 15 minutes of using this new baby, I just got to love the keyboard (which I otherwise hated, having tried it once last year in store and thinking it was no good at all). I thought at first that I would have to re-learn how to type on a computer, but after getting used to it quickly I can definitely say that I am so much faster and precise when typing. It really helps to have the keys a tad bigger, as I am no longer pressing in between "islands" and hence typing precision is tremendously improved for me. I am actually seriously thinking of keeping this rMB and sell my 15 inch beast, which I rarely used at its full capacity. And also, having a flat keyboard like this eliminates the problem I had with my 15 inch model, so it's definitely a lot better built from an engineering perspective.