First safe: You create a document and want to safe it or the first time. That causes LibreOffice (on my machines) to beachball for up to 2 minutes. Saving changes to existing files work fine. This problem is existing since the last 3-4 versions or so.
Boot time: Yes, startup time. Time untill you can actually start to write is quote long with up 40 seconds.
This problem exists like forever. I do not consider it as a bug - still: even MSWD is way faster.