I use LR4 (well, C1P for my Sony files, but LR4 for the thousands of still unprocessed Canon files I keep coming back to).
It's got a slow interface. A bit more bearable now that I upgraded my desktop, but still slow.
I know there are ways to speed it up, and played with some of them. My question is, though, is LR6 any faster on the same machine with same settings than LR4 ? LR5 by all accounts wasn't.
Also, does anyone know if there's an upgrade price for LR4 users ? (AFAIK they still offer a non-subscription version).
Any particular improvements in features that would make me want to upgrade ?