I've been using LR 4 (actually 4.1) for a month or two and had a feeling that I was getting much better results than I did with LR3 (3.6).
I quite often review old files taken in the past six years (when I switched from film to digital). This is done on the premise that my processing skills are getting better. Well that could be part of the solution, but I felt there was something else going on - particularly in the darker areas of an image that at times tempted me to try HDR. (I even have an exposure setting programmed into my camera that automatically takes three consecutive shots - one underexposed, one proper exposure, and one overexposed with the intention of combining/blending them.)
As some of you know , I'm keen on ETTR - which means that I push the exposure as far as I can to result in either no clipping, or minor clipping of the highlights (there is no method to preserve specular highlights and still retain a reasonable exposure - with one image). There are images however where the left (dark) side of the RGB histogram is still in the shadows with little visible detail.
Recently while reprocessing a number of sunset shots taken a year ago on the Oregon Coast, I felt that LR4 was doing a considerably better job than LR3. Until this morning, this was just my impression, albeit a firmly held one. This morning, I blundered onto this:
Reading this, the light came on - literally. Actually the lights came on when I learned how to use the SHADOWS slider (and the HIGHLIGHTS one too), but the SHADOWS one is dramatic.
Not only does LR rescue the shadows, the author also states, "gives slightly more highlight headroom, and can do a better job of rescuing overexposed images".
There is much more to the article, which I've barely gotten into, and will spend some time digesting, but the bottom line is that I'm very pleased with the increased power of LR4 over that of LR3.