My only real complaint about shooting mft exclusively, is that the noise level starts getting especially noticeable at ISO 400 when I bring up the shadows in post. My rule of thumb is whatever I print has to look clean at a minimum of 25" X 18." Otherwise, to me, the file is worthless. I have discovered workarounds that sometimes help. Topaz Labs Denoise 5 is my goto PS plug-in. It does, in my opinion, handle noise reduction better than ACR and the noise reduction filter in PS6. Is it perfect? No. There is no substitute for shooting at base ISO with mft.
The EM-5 II produces clean ISO 800 files in multi-shot mode. The thing about Oly files shot at base ISO, is they are gorgeous, of course using good glass is a given. I've made some stunning 24" X 32" prints.