Haven't tested it yet, apart from the white balance picker which now does what it was advertised to do in the beta: Sample the whole loupe area.
I've wanted this for ages, and it makes the picker super consistent! It may seem a small improvement for many but I love it.
I also love the fact that a load of Tokina lenses now have official lens profiles. I have used a home made (by someone else) profile for my Tokina 11-16 mm, it will be interesting to try out the included profile.
Yes, I agree, and performance is - contrary to the beta - very good so far. I would rate it subjectively as quick as LR 3.6.
Great product, great job by the engineers. To me a much better upgrade than LR 3 ever was.
Have any posters as yet tried LR4 with the upgraded preview file, and then tried deleting the catalog preview file (XXXX Previews.lrdata) and seeing if there is a speed improvement.
I'd be interested to see if using a clean previews file also helps with the speed improvement as it did for the transition from LR2 to LR3