I have an image in LR and I did send it to PS and did some editing. I'm noticing that when I flip between the Library and Develop modules that the image displays darker in Develop. Flip back to Library and it brightens up.
On the latest versions CC 2015
I also just noticed that the Print module seems to show the image brightness like the Library module. So now I flip between the 3 and a couple times they all looked the same, the darker version, but if I slowed down it seems fairly consistent that Library and Print match and are brighter than Develop.