Our office runs a document automation package called LEAP which connects via 4D Client.
I've installed 4D Client under a Debian machine using the last couple of versions of Crossover and it seems to work well. We don't often use it from this machine but when we do have not noticed any problems. It connects to and displays from the database with no problems and successfully generates and opens word documents using Office 97 or 2000 under Crossover.