My conclusion after a few days: Currently I see no reason for me yet. Although LR6 runs quite smoothly on my machine, but the promised Adobe high speed up very LR6 is not recognizable. The graphics card for GPU support was recognized easily and is also used ange (eg. 1: 1 previews).. I suspect, however, that the built-in SSD is here responsible for the good values to the RAM as well as already under LR 5.7.
LR 5.7 I use on a Macbook Pro 13 with Intel Core i5, SSD and 16GB RAM. Here was and is for me a significant difference in performance to the Windows system recognizable, called LR 5.7 works with Apple clearly better together. Whether this under LR 6 also is not so, I could not even try.
On Windows computers, I can (for example using a brush, importing, exporting such.) Recognize when LR6 LR 5.7 to a slightly smoother working in the Develop module and the Library module. But what never occurred in LR 5.7, is the short-term rebounding from LR 6 in Develop module in the full-screen display (F) to Normal. Here me the previous image and not the current is displayed for a brief second. But I believe with version 6.1, this could already be fixed.
The new features such as face recognition, etc. I find though "nice" but not be a compelling reason to move. It is the new face recognition is in my opinion not quite on the level as at its competitors. Again, while the performance of my computer surprisingly good (1,000 images without video files were approximately 2-3 minutes; with videos, it takes significantly longer depending on the length), but the results are in some cases also quite fun. LR6 recognizes partially in macro photography of plants and in building photos also faces. How fine it reacts partially shown by the example of a photo, in which a person holds an expression of a family photo in hands. She holds the photo diagonally and with light from the side. At the family photo 20 people are sometimes more bad than good recognizable. Nine of them has proposed me LR6 in face recognition as a new face! Respect.
For now, however, I shall stay with my LR 5.7 and use it as usual with a lot of joy.
My computer configuration is as follows: Windows 7 (Professional) 64bit) Intel Core i7-4790 4x 3.60GHz, GIGABYTE GA-H97-D3H, GeForce GTX 750 Ti 2GB GDDR5, Kingston SSDNow V300 240GB, 16GB RAM ELIXIR / Crucial.