Another LastPass user here. The two big obvious ones:
- Completely non-standard menu behaviour and appearance
- I to this day can not associate the shortcut icons for copy/edit etc. with the password. Maybe that's just m..
- The one single function I use the most often is "generate password", and it's hidden one menu down from the root.
- The second most frequently used function for me is to view the password, when I need to enter it somewhere where I haven't got Lastpass installed (on another device, so copy/past isn't sufficient), yet that requires me to click on the site, "edit" and "show password".