Jerry,
Use the Linux version for sure, it is rock solid.
As far as backups go, you can use gbak via a chron to do it whenever
you want. Backing up and restoring compacts the database, but you
don't need to do a restore very often. Firebird is very low maintenance.
I would highly recomend it.
If you need datetime,math and string functions you can use the
FreeUDFlibc, we just used it in a pretty big project that has about 9
stored procs.

The linux version is missing the FBUDF library however, hopefully that
will be available soon.

Tony Caduto