the best analysis Ive seen suggests about a stop better than GH2
OM-D Read Noise - 1EV better than GH2?!!: Micro Four Thirds Talk Forum: Digital Photography Review
looking back at DPRs somewhat disappointing GX1 review, I think this is quite a bit better than most of us had hoped for
and since the noise performance seems to have been realised, what then for the DR claims
lookin good...