After using the new re-designed Basic controls in the Develop Module of Lightroom 4 Beta for a while it's beginning to sink in how great these improvements are. In particular I'm talking about the Highlights and Shadows sliders.
Everyone that has ever shot an interior shot with bright windows has dreamed of having an slider that controls the exposure of the windows and one that independently controls the dark corners that every room predictably ends up with. Well, now you can do exactly that! The new Highlights slider lets you darken just the highlights (usually the windows) and the Shadows slider independently lets you lighten the shadow areas (usually the dark corners). The other amazing aspect of they way these work is it appears to work just as well with JPGs as it does with RAW files.
The old Recovery slider in LR 3 used to do this a little but the amount it could help drop the exposure of the windows has always been disappointing to me. I went back to a view listing we had a number of years ago where I had to end up masking the windows to make the client happy with the way the view showed through the living room windows and I was amazed by how much I could control with window exposure with just the Highlights slider in LR 4 Beta. These new sliders won't always eliminate the need to mask windows to get a perfect view but they make a huge difference compared to the old Recovery slider.
I think these new controls are worth the price of the update to LR 4 all by themselves. They are a game changer.
The other slider that looks that same but works WAY better now is the Clarity slider. To my way of thinking, almost every image can benefit from some added Clarity. Problem has always been if you go too far halos would always start appearing. Now that's gone! No halos! Use all the Clarity you want. Over doing it on Clarity now just gives images sort of a HDR look.
It's best to try these sliders out on your own images. You can get a free copy of LR 4 Beta here. Also, if you just want see a quick detail description of how these new sliders work go checkout the free LR 4 Beta video at lynda.com. Chris Orwig gives a really nice detailed walk through of all the new features of LR 4.
Update 2/20 9:30 Pacific: For Mac users, commenter Rochelle below raises an excellent point. Aperture 3 (released Feb 2010) has had this Highlight/Shadow slider function, which actually appears to work better than the implementation in LR 4 Beta, for two years. One could easily argue that all the items being added to LR 4 will make it almost equal to Aperture 3 which is less than half the price of LR. If I had to make a wild guess regarding the next version of Aperture, I'd guess that it would be out real soon and will jump way beyond LR. Just a guess.