solutions for new Postgresql application testing

We are going live with a application in a few months that is a complete
rewrite of an existing application.  We are moving from an existing
proprietary database to Postgresql.  We are looking for some
insight/suggestions as to how folks test Postgresql in such a situation.

We really want to run it throught the wringer before going live.  I'm
throwing together a test suite that consists of mostly perl scripts.
I'm wondering what other, if any approaches folks have taken in a
similar situation.  I know there's nothing like a real live test with
real users, and that will happen, but we want to do some semi-automated
load testing prior.

Anyone ever use any profiling apps (gprof) with any success?

We've got a failover cluster design and would like any insights here as
well.

We're also trying to decide whether a single database with multiple
schemas or multiple databases are the best solution.  We've done some
research on this through the archives, and the answer seems to depend on
the database/application design.  Still, we welcome any generic ideas on
this issue as well.

I've not provided any specifics on hardware or application as we really
want high level stuff at this time.

Thanks for any pointers or suggestions.

--
Until later, Geoffrey