My 4+ yo Dell is starting to struggle in LR with my larger D600 files . . .. I'm considering getting an Imac both for the display and other issues. Can someone give me some insight into transferring LR libraries from a PC to a Mac? What issues am I likely to run into?
No issues. Move the catalog over, move the files over. Done. At worst you may have to reconnect the folders to the catalog, but that's painless if you're wisely letting Lightroom organize your files for you.
If Lightroom isn't organizing your files for you, you should only have to reconnect as many master folders as you have. For most people that still ends up being a single folder and so still quite painless.
Best to have a master folder which has all of the images and any image-bearing subfolders beneath it. Then copy that entire structure across so that you only have to point to one master file. Doesn't matter where you copy it to - i.e. that master file can be at level in the hierarchy on your mac.
Just carefully consider everything else before switching to a mac, so that you can inimize any pain. Don't forget those things you've been taking for granted such as rarely-used utilities.