It appears the new LR 3 beta includes a new demosaic algorithm and sharpening algorithm. The amount of detail you can extract from the images has gone up by leaps and bounds. You can also go much farther in sharpening than before without the image starting to look like a waterpainting. One nice thing too is that you can also inside LR 3 beta, select the old rendering engine to directly compare. The option is in Develop in the Settings menu, submenu "Process Version". Below is a quick example of the huge difference in detail. This is a scree slope somewhere in Rocky Mountain National Park, so lots and lots of fine detail. The image below shows the LR 2 version. Mouseover for LR 3. You might have to wait a few seconds for the second version to load. Also note that since these are medium-high quality jpegs, some detail is lost in the jpeg conversion.
When I have some time, I'll provide some more analysis. For now, it is looking very very good.
UPDATE: The above image but scaled to 200% Here you see that the new algorithm will really help very large prints (the full image below would correspond to a print of 4x6 feet!. The mouseover version (LR 3) is obviously far better as it doesn't show the weird watercolor effect that you can often get in LR 2.
Here's another example.