I've just recently started using Lightroom and Photoshop CC 2015 for my photography (hobby) work. I first started using Lightroom on two desktop PC's (I'll list the specs below) which is pretty painful to use. Importing and exporting files to/from Lightroom works fine and using the option to Open in Photoshop works fine when that need should arise. The problem I've run into is any editing with brushes, gradient filter, etc is horribly slow. I can take the brush to make an edit, swipe across the screen and it many cases count 1, 2, 3, 4, 5, ,etc before I will see the change on the screen. These changes could be very small or something large, doesn't seem to matter.
Now, I my new MacBook, Lightroom seems to work perfectly fine. This is really my first Mac so I'm not sure how the two software packages compare from a performance standpoint.
My Main PC specs;
Asus Z87 Motherboad
Intel i7 quad core @ 4.0Ghz
32GB RAM @ 1600Mhz
Intel 512GB SSD
NVidia 760 series Video Card
Windows 10 64bit (Already reloaded 10 and tried Windows 7 as well)
Lightroom catalog and RAW files run from a RAID 1 drive set (2TB at 5400rpm)
Intel i7 2.8Ghz
16GB RAM @ 1600Mhz
Slowdowns using a lot of brushing and spot healing is a well-known problem in Lightroom. There are several (partial) solutions, you can try one or several or all of them as needed
I do not work for Adobe, and so my opinions may not be their opinions, however it seems to me that the non-destructive editing technology that they have invented and use in Lightroom/ACR reaches a limit of capability with a lot of brushing/spot healing where the hardware cannot keep up (but it works great for all other editing)