Do go ahead
Just keep in mind that so far most of the ones who've invested into the 12-40mm see it as a worthy investment. Peace of mind is definitely impt.
One thing that is an improvement in the EM-1 is :
'Fine Detail Processing 2 (FPD2) is implemented in Olympus' latest image processing engine, the Truepic 7. The benefits of having the FDP2 is being able to create flaw-corrected, optimized JPEG files, straight out of the camera. FDP2 applies various corrections and compensations on image property flaws (chromatic aberration, loss of resolution due to diffraction, etc). We all know that software correction of distortion and chromatic aberration are not unheard of, and have been widely implemented on newer cameras and lenses, but
Olympus took a step further by having the E-M1 to recognize each individual lens separately, and apply the relevant corrections in correspondence to that particular lens only. Each lens profile information (applicable to Olympus lenses only) has been stored within the E-M1, and as the lens is used the FDP2 will adaptively correct the lens flaws. Also, the level of JPEG sharpening will be applied varyingly depending on which lens being used. Obviously the lens sharpness of a macro lens, such as the M,Zuiko 60mm F2.8 macro will be a lot better than, say the kit lens M.Zuiko 14-42mm F3.5-5.6, thus practically less sharpening should be applied on the images taken with the macro lens.'
lifted whole-sale from Robin Wong's website.
You can easily find a good prime in MFT, some are the O75/1.8, O45/1.8, O17/1.8, P25/1.4, P20/1.7 to name a few.