As much as I'm looking forward to Vivaldi Sync, it will only solve half the problem. Like @Catweazle, I'm also using Xmarks Sync on all of my computers. The advantage of it is that it also syncs with Chrome, Firefox and IE (no Edge yet). So I guess I'll still have to keep Xmarks in order to sync my bookmarks with other browsers. I'll drop Chrome soon but I'll still have to use some of the Microsoft ones in certain cases.
A function that would save me a lot of time would be import/export Vivaldi settings for installations on different computers. I'm spreading Vivaldi on all my client's systems but configuring them is a pain. I know, I'm copying some of the settings files but it's not clean and complete.