Warning: extreme pixelpeeping alert! You are not going to see any difference if you don't print extremely large.
Now I've give you the disclaimer, I want to say that I am really quite impressed with the new demosaic in Lightroom. I posted one example before where you could see the subtle effect that made the LR 3 images look more natural and allow for larger prints. Here is another example where instead of using the same sharpening settings, I tried to optimize both the LR 2 and the LR 3 version. It is not possible to get the LR 2 version to show anywhere near as much detail as the LR 3 version. The LR 3 version also looks far more natural and less fake. Surprisingly, you can even see the effect a little bit in the scaled down version that I use below as a placeholder. Full-res version in the link where you can really see the difference.
Of course, the left is LR 2 and the right LR 3
Edit: David Naylor comes to very similar conclusions on his blog.
Edit 2: This is the lower right corner of a frame shot using the ultracheap Nikon 18-55 mm kit lens. Parameters: Nikon D300, 18-55mm f3.5-5.6, ISO 200, f8, 1/60 s, handheld. It always amazes me how sharp this cheapo lens can be.