Where I work we have a PMO; its not called that, which is good, because it's not a very good PMO.
Why not very good?
Because it is an information one way street. We all provide data on our project timing, but never see a consolidated report to enable us to link up projects, reduce redundant deployment of resources and people (note, resources are not people, and vice versa), and generally get more efficient. But it doesn't happen and currently we have three projects doing overlapping data remediation actions using the same big database!
In the old days in my firm we had a more organised system than currently for keeping the execs on top of what was happening. A quarterly report was done in a standard but awkward format (some genius has crafted tables within tables in Word! Not good; and there was no calculation on any numerical or data data) and submitted to an exec meeting.
The report was not as useful as it could be but, at least the executive committee could compare and line up projects with each other, which they did in part, but not thoroughly due to they didn't fully understand any of the projects reported!
A PMO should make connections, bring people together, and overall save money while improving project portfolio returns, otherwise it is just a template shop.