Performance/Reliability statistics?

To start this in the typical I-just-joined-this-list fasion:

Hello, all:

I'm pitching a project for a client currently and have narrowed the choices
for the back-end down to PostgreSQL vs. InterBase vs. Oracle.  InterBase and
Oracle both have basic performance and reliability statistics (InterBase says
it's good for about 700 users and about a 10,000 row database, for example),
but I have not been able to find any such information about PostgreSQL.

I know that any such information would be subjective, but I'm looking to make
sure that PostgreSQL is in the same ball-park as the project.

This is going to be a PHP-written web-based application with approximately
2000 users which come in two classes, the first class (which is about 1900 of
the users) will usually be using the system once a day, maybe in the morning -
maybe not even that regularly.  The remaining 100 (well, less than that
actually - maybe 50?), will be using the system constantly between 7AM and 5PM
every day.  The database structure is going to be medium-sophisticated but it
will really revolve around two or three tables, the most central table will be
indexed multiple ways and heavily read and updated simultaneously.

Okay, do we have any statistics on a somewhat-similar environment?  I love
PostgreSQL, so I don't mean to offend anyone by saying this, but I really
haven't seen it used in this scale environment...  Anyone?  Tricks to keep
it running? (I noticed on another list that a backend horking causes the
others to rollback and shutdown to avoid corrupting shared memory, so I'll be
putting this into inittab ;-)

Thanks in advance,
-Jason M. Felice <jfelice@cronosys.com>

P.S. If there are some good medium-large-ish scale projects which are fairly
stable out there, the next step will be to ask how much hardware.