All my pictures are processed in Lightroom and I was interested to try out the recently released beta version of Lightroom 4. The new tone controls were a bit strange at first but with a bit of practice they become intuitive. The issue I do have is that it is slower than LR3, it likes to use lots of memory and sometimes grinds to a halt! However, I see from various comments on the web that the speed is expected to improve once the final version is released.
The following shot has been processed in both for comparison purposes. It has been heavily cropped from a Canon G10 image taken last week.
LR3
This shows that with some practice it is easy to replicate in LR4 a LR3 processed image.
Another example:
LR3
LR4
In this example (another G10 shot) LR4 handled the highlights much better while preserving greater detail in the shadow areas of the wooden carving.
So far I like the way it handles images and I hope Adobe can address the speed issue in the final release.