Josh Berkus and Sun have put together the first real PostgreSQL performance benchmark. I run into people often who are still working under dubious performance comparisons done years ago against against competition like MySQL and Oracle. Hopefully this in depth comparison will put some of these arguments to rest.
If you're just interested in the conclusions, PostgreSQL is as fast or faster than MySQL and nearly as fast as Oracle. I know the performance improvements over the last few years have been nothing short of phenomenal, glad to see there is now a report to back up my gut feelings.