I haven't really had a chance to explore 3.0, but I'm also disappointed at the lack of a lens correction feature. It would be nice to get rid of PTlens and keep everything as RAW data in the one application.
Soft-proofing is not a feature that really affects me (though it can be useful to see when I've clipped saturation vs colour simply being outside my monitor's gamut) but it will be very disappointing if it doesn't end up in 3.0. I suspect it will be there though, maybe just not in beta 1.
That said, image quality seems drastically
improved over Lightroom 2, at least with the high ISO images I've had a look at.
Here's a 100% crop from an image that was particularly bad in Lightroom 2:
And Lightroom 3's rendition:
It's a smooth white wall being hit with two different coloured lights, if you're wondering—I'm sure people will find much better examples, this was just an image that I remembered looking particularly bad.
This is with zero sharpening, no luminance noise reduction and 20 chroma noise reduction in each. All I did was import the image into Lightroom 3 and enable the new processing.
In the past I've also had quite a lot of images from my 1000D that showed a very obvious pattern in Lightroom 2, hopefully the new demosaicing will have removed that as well.
The only downside I've seen so far is that I'm going to have to redo my sharpening presets as it looks completely different now. (but it seems like it will be better)