Thanks for that. I have been doing a lot more experimenting with LR 4.1, and the two process versions are certainly very different. Which makes it difficult to make direct comparisons, as you say. Some thoughts -
* PV 2012 will retrieve a touch more highlight detail in my 3FR files. At first you think it is retrieving massive amounts more, but that is because the top end of the file is already very compressed when imported into PV 2012. In fact, you can get pretty much the same result in 2010 with recovery and grads, etc. Not quite, though, and LR4 wins here.
* The fact that the highlights are already so compressed is not necessarily that helpful in B/W work. I prefer the more linear rendition of PV 2010. Some of the "pop" has been taken out of the image and I find myself putting it back in using the White slider.
* There seems to be no real equivalent for the Brightness control in LR 4. Exposure does sort of the same thing, but it does not peg the ends of the histogram down like Brightness does. I use Brightness a lot (for reasons which I will explain if you like and won't get bored).
* If you are working in colour where you really need shadow detail, no blown highlights and no hue shift when editing then PV 2012 is brilliant. I tried a few colour images and there was a clear improvement. But for my B/W work I am not so sure.