No new features other than camera support, but I think it's good to always run the latest version (sometimes there are bugs fixed that weren't mentioned, and sometimes there are subtle performance improvements..).
If you ever have a problem in Lr5.6, you won't wonder whether it's also in 5.7, nor will others if you report it etc..
If you have bad luck with latest version, you can always downgrade, but it's highly unlikely you'll have to do that..
If LR 5.8 is the next version it might have more bug fixes, but if LR 6.0 is the next version it might have more bugs, right?
If you ever upgrade your OS to something more current, you’d probably want to have the most recent version of LR.
Thanks all. Much appreciated. I'll go ahead and install update.