Diane,
I had lot of DSLRs over the past years (E1, D2X, D200, D300, E3, A900, D700, K5, 5D2) and I also bought into M43 last year with the EP2. I think I said that already earlier, the best high ISO performance of all these cameras has the D700 - no wonder - right? I also can attest that there were issues with higher ISO especially with the E1 (of course) and the E3, as there were with all the older designs like D2X, D200 etc. But from the range of current "state-of-the-art" DSLRs the GH2 performs very well - I would say it is in the top range WRT high ISO - I am talking of high ISO in a range between 1600 - 3200. And I only am using RAW - NO JPEG out of camera.
With that in mind you should not be disappointed with the GH2 I guess. Are there better performers in high ISO? Sure there are. But for a small and handy and light weight cam like the GH2 the results are stunning.
If Olympus had incorporated the GH2 sensor in the E5 instead of the older 12MP chip all together with their new "xyz-picture engine" and weak AA filter, I would have switched back to Olympus without any further thought - so excellent I find this new sensor in the GH2.
I can say nothing negative about this camera and I am usually very picky! Will there come a better camera in the future? Sure! Will I then buy this one? Most probably!
But for now the GH2 is the absolute optimum in my eyes WRT size, weight, usability, IQ and price ... did I forget something?