The E-3 does sound nice, and I cannot wait to look through the viewfinder with the new f2.0 14-35mm zoom they also announced!
In regards to the sensor size question, which comes up all the time as I talk to my Canon and Nikon using friends, I have to ask: why do you care? Some people like to use wide angle lenses, and they do not want a total loss of DOF control, so large sensor size makes sense there. Some people really need superlative low-light shooting ability, again a big win for large sensors. Other have a bunch of existing lenses they want to use with no conversion factor, and that makes sense. But if you are happy with the angle of view of the four-thirds lens offerings (from 7mm up to 500mm, or 14mm to 1000mm in 35mm equivalence), and are content to shoot mostly at ISO 400 or lower, and don't need to continue using existing lenses, then I'm not sure the substantial expense of the full-frame sensor is worth it.
For me, the sensors of my E-300 and Lumix L1 are the right size. The image are big enough to make nice 16 X 20 inch prints, even with some cropping. The overall image quality is really to my liking. There are a million reasons to choose a particular DSLR, but be careful on the sensor size issue, as for many people it is not the 'big' factor. Then again, for some it is a 'big' deal... What counts is making good pictures, and the four-thirds system definitely helps me do that, even with the relatively small sensor. Fact is, I wouldn't want to move to another system just because of the sensor size. I might consider moving to Nikon if I keep having to shoot at night though, as the current performance on the four-thirds sensors above ISO400 is not what I would like. But so far the number of times I have to be at ISO800 or (God forbid) ISO1600 are few. My hope is the E-3 is a bit better than the current line-up in terms of noise and shadow detail at high ISO settings.
Cheers! - marc