I second this. I'm using a just-refreshed 12" Retina MacBook ‘toy’ (BTO m7/8GB/512GB) and it is an utterly perfect, ‘nervous’ little machine that suits my varied computing needs perfectly (local databases, spreadsheets, data exploration, symbolic mathematics in Mathematica, general productivity word-processing/email and assorted browsing & multimedia). This is a machine that deserves respect.
Is this one of the new macbooks? I'm strongly considering doing exactly this but figure at this point I might as well see what they have in store for MBP, or even MBA if they don't can the product line.
I am running IntelliJ IDEA Ultimate and Visual Studio 2015 Enterprise (in a Windows 10 Fusion VM) without any issues.
The lightweight portability and 12" retina screen are amazing.