Going to echo this sentiment. The project I'm on now is the first time I've worked with a PM that gets whats going on and actually manages the product instead of just sending PMs after hours asking for some "small" feature to be squeezed into the sprint. It makes a HUGE difference, and I can honestly say I'm much less stressed out now than in previous projects.

interesting. i've cycled through some projects with and without PMs. I've not found 'good' PMs to make a huge difference compared to 'without', but definitely 'bad' PMs impact things negatively. It's hard to define what the 'bad' is, but micromanaging, forcing process where it doesn't need to be, arbitrarily enforcing rules when convenient, etc are all just negative impacts. It would be more beneficial to just not have that person at all. I've had some good PMs, and while I didn't notice much difference in my own performance/delivery/stress/etc, I think it gave some other folks somewhat more confidence/assurance.

As someone else eloquently put it, "With people management, the ceiling is low, but the floor is lava."