It was quite frankly the most productive custom business software package I have ever used. Literally would take 10 people a week to do something custom you could do in an afternoon with 1 person in Access. I suspect the same is true now.
SQL Server was a crap load easier to back up reliably
In a lot of cases, I've found it to be the best tool for a temporary or one-off (preferably smaller scale) data mining/massaging project. The query-building interface was the way I originally learned the basics of relational databases, and it also helped me get a better grasp of SQL-- the ability to flip back & forth from the GUI query builder to the SQL it generates is nice.
On the multiuser side, however, I have found a couple workarounds in the past. If you have everyone operate locally and space out their central database connections to intermittent, automated burst queries, you can get more concurrent users than you might expect. It helps to have fewer users per table, as well, and of course it really helps if they don't need to see the most recent adds/changes in real time.
[https://en.wikipedia.org/wiki/Microsoft_Jet_Database_Engine]
Access is really meant for single-user scenarios I feel. Maybe the locking mechanism has gotten better but for multiuser access I tell people to use a real SQL database.