The E-30 is out today, at least in Japan. I stopped by a few camera stores today trying to figure out my next steps and Olympus was front and center in the all the stores. I don't have an E3 so I can't say too much about the differences.
It's a bit smaller and noticeably lighter then the E-3. It's a little shorter which I like. The view finder is slightly smaller then the E-3, but still a huge improvement from the E-xxx series. Most of the changes you've read on the previews. It really does look like an E-3 without the weather sealing and a few new features. I imagine the successor to the E-5 is going to be a bigger step up, although I'd miss a cheap sealed body.
They had some photographers from Oly there to talk about them. According to them the improved sensor has an extra stop in the highlights and gives it a little better DR then the D300. ISO sensitivity is supposed to be a stop better then the E-3, so if you weren't happy with ISO 800 before, you should be now. I do like the contrast focusing in live view. Very nice. I hope they make some of their older lenses compatible, even if they are a bit slow.
Some small stuff. I'm not sure how big of a deal they are. You are supposed to be able to tweak the focusing on a per lens basis (to fix front and back focusing issues) and the E-30 remembers up to 20 lenses.
The level gauge in live view is pretty cool. The multiple exposure was kind of cool too, although you could do the same thing in photoshop and with more control. The auto gradation is supposed to help deal with highlights and shadows, although I couldn't really play with it in the bright store.
I'm hoping the information about the sensor is true. I'm sure some reviews will be popping up soon on the Japanese sites.