Is the EM5’s Miss-Stated ISO concerning to you?

You should recheck that. DXO Mark indicates that the E-M5 is at least 1 stop off from ISO 800 through ISO 25,600. In addition it is so close to being 1 stop off from ISO 200-ISO 400 that you should have said 1+1/3 EV worst case(Stated ISO 25,600 - Measured ISO 11,848).

I know Dpreview shrugs this off. However, I have seen no indications that it is only 1/3 of a stop difference. Every picture and test shows that it is closer to 1 stop understated for the E-M5 and that the GH2 was dead on.

If you compare the GH2 at ISO 3200 to the EM5 at ISO 6400 the difference is not so significant.

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GH3, Hacked GH2, and Full Spectrum GF1 Sample movies
http://www.youtube.com/user/mpgxsvcd#play/uploads
GH3 Tips and Tricks
http://www.youtube.com/watch?v=hIMdxoGbNXU
GH2 Setup Walk through
http://www.youtube.com/watch?v=uROQbbiiO2I
http://vimeo.com/user442745
GH3, GH2, GF1 Pictures
http://www.dpreview.com/galleries/4222674355/albums