I've used Notes. It is more of a document management system that an RDBMS.

If you are storing documents then, obviously Notes is the way to go. Incidently I know someone who has a Notes front end to a SQL database.

The only thing I have against Access is that it can cause locking problems when used as a front end to a server database.

Basically I've used most PC databases since dBASE II/Clipper and one or two old mainframe hierarchal databases.

Moving up to server databases has been a revelation.

MySQL has its fans though personally I suspect the MySQL vs other open source databases is the VHS vs Betamax thing again.