DSLR Check, as is frequently the case, is the first website to post an ISO comparison of a new camera. The camera of course being the Olympus E-PL5. The camera performs identically to the E-M5. Both cameras do very well in retaining detail up to ISO1600, but ISO3200 and 6400 show significant loss of fine detail, with many areas turning into smudges of color.
Neither camera quite stands toe-to-toe with the compared Nikon D3200. It's close, and there seems to be less difference at 6400 than 1600 or 3200, but the difference is there. This is expected, seeing as Nikon really pushed boundaries by putting Sony's already-legendary 24Mp APS-C sensor in what's essentially an entry-level SLR.
Granted, this is almost not news. I don't think anyone was really expecting the E-PL5 to perform much better as regards noise. The really juicy information is the supposed large increase in dynamic range. We'll have to wait for some more tests for that information.