I\'m using delphi for years, but never for database stuff, but recently started researching and testing.
I must say, i\'m impressed, most of things happens automatically
@arthurprs, for you scenario
(2 layers) 5 user computers, 1 > database server.
alt text http://www.techsolusa.com/images/firebird-logo-64.gif The Firebird RDBMS is a very good option , because is very stable, fast, runs on Linux, Windows, and a variety of Unix platforms and meet with you requirements.
alt text http://d.yimg.com/kq/groups/12858579/homepage/name/homepage.jpg Respect to the components for connection i go for ZEOS.
I have used this combination in many small and medium projects, with excellent results.
I have worked on many commercial high volume systems using ADO without any problems. Deployment is relatively simple since its included in the OS. Since it has such a wide audience, most of the major issues have been identified and corrected. Getting help with ADO connectivity is very easy. The database support is very deep (connectionstrings.com) which make supporting additional database engines almost trivial (you may need to still install the client drivers, but that would be the same for almost any solution).
Performance isn't much of an issue, it really will come down to database architecture and engine selection.