In my experience: working with a good or great PM is fun and productive. Working without a PM is ok. Working with a bad PM is somewhere between irritating and infuriating.
Development was so much smoother. I didn't have to spend time explaining why we couldn't do this or that. He'd nix bad ideas at higher levels before it even hit us. We were given ample warning on how we approach things ("Custom B will want this, and if box what you're doing now it'll be harder blah blah blah").
Those PMs in the PMO knew their shit, they were realistic, they understood different strategies, they handled managing up and down, and ensuring everyone knew what they had to do.
I wrote a linkedin review for my favorite PM and it's as follows:
When I first met Rajitha, she was in the process of managing a company wide Windows 7 to 10 upgrade. As it turns out I was one of the last holdouts and was badly overdue. She was incessant! I hated it!. Finally, I gave into her demands and as these things go, I was pleasantly surprised how smoothly it went.
Fast forward a few months and Rajitha was tasked to work along side myself and others on several complex tech merger/acquisition projects. Moving parts, moving people, the whole thing was a whirlwind held down by a few important people on the team, including her. My initial resentment was replaced with a new deeply held respect for her capabilities and skillset. She was amazingly diligent and focused, friendly and compassionate.
If you're get a chance to work with Rajitha, count yourself among the lucky few!
Sorry Rajitha, this recommendation is many years overdue. I was cleaning out my filing cabinet and found a stack of old Church & Dwight papers. A print out of "How I learned to stop worrying and love Direct To Consumer". A "Magneto", not "Magento" project cover, and a handwritten note -- left on my desk -- from you to make sure I followed up a task that was in my queue".