With the most recent update, the links in the upper right hand corner have been converted to icons and the links to [[Special:Watchlist]] and [[Special:Contributions/<User>]] have been hidden away in a small menu:
Previously, they were directly accessible:
For me, the link to the watchlist is by far the most-often clicked link when editing Wikipedia. It's what I click right after I log in and whenever I'm done reading or editing an page and want to move on to the next task.
Based on my experience watching experienced and instructing new editors, I'm very certain that this is quite common among Wikipedians, whether they are new to the project or regulars. I personally also use my user contributions to access the pages I have edited recently and to follow-up on discussions, not sure how common that is.
I really like the new Vector layout with the fixed width and I appreciate the idea to clean up the interface, but this change breaks a common workflow. The watchlist should be a first-class link that is always visible and easy to access.