More Arc features I found today that I like:

If you click a link in a pinned tab, it shows you a preview in a lightbox instead of automatically opening that link. (Links in unpinned tabs work exactly as you’d expect).

Command + Shift + C copies the current URL, and they try to strip tracking info off.

Air Traffic Control lets you decide which space a link opens in. For example, all WordPress.com URLs now open for me in my Automattic space.