I've just compared results of the same shots (at our local camera shop) using my E-300 and the E-330, with my 14-54mm lens, into low light areas. By mistake I shot jpg in the 330 and raw (my default) in my E-300. One thing that I want to see improved is high ISO performance so I shot at 1600 in both cameras. The other thing (given that I shoot people moving around in fairly low light) is focusing. (I've been carting around both old manual focus Nikons and the E-300 for this reason; I can focus faster with the old SLRs.) One hope I had was that the LCD screen would help in focusing; I gather it may be too dim in bright light but that's not my worry. I also think that the mode B which allows a blown up focus area (with shutter lock up) may prove invaluable; I haven't tried it yet.
This is most unscientific - Shutterbug will get it straight - but there is no question that the E-330 shots are much, much clearer even though they're jpgs up against raw. There is certainly noise at 1600, but as I always convert to B&W I don't think it will be an issue for what I do. (I'm also looking forward to the Sigma 30mm f/1.4 coming out in the Oly mount.) I guess I might add that with Genuine Fractals, I see no need for more pixels, just better pixels. I know it makes sense to wait for the price to drop but I'm not going to.