PostgreSQL in mission-critical system

We are currently designing a system for a client, where the database will
hold mission-critical information, dealing with money. Needless to say the
requirement on the database are very high, particularly regarding data
safety and reliability. In production we see that we will probably need a
solution with two databases running in the same state.

The system architecture will be based on J2EE with a JBoss application
server.

Any views on the suitability of PostgreSQL for this task? Should we rather
go for a commercial solution? Any experience?

rgds,
Rune