The default search behavior, IMO, should be to prioritize matches in the title field over those in other parts of the metadata.
Currently, paperpile sometimes returns results for which search terms match parts of the abstract, etc. over those for which all search terms appear in the title.
This is probably not what the user is looking for.
If you already know the exact title of an article you want to find, just typing part of the title should quickly find & show that match at the top. At present however, I can literally input a complete title and still have the article lost in a sea of irrelevant search results.
Related: +1 for exact searches with quotation marks