Hey Rich,
I'm only at 21 units (closing on another 4 next month), but I work a full-time job and also got my real estate license this year, so my plate's pretty full.
I've been thought about hiring a PM company for a while now but I've decided to keep the management in-house.
I think it's important to start delegating out the low dollar per hour tasks. If you don't have a virtual assistant yet, I'd recommend getting one to help with things like tenant communications and coordinating contractors. They can take care of a lot of the monotonous tasks, and even do things like send leases, screen tenants, add rent charges, pay utility bills, the list goes on.
Another thing I've done is hired my fiancée to help with things. She works for me several hours a week and it's been a good way for her to learn the business, make some extra money, and help me with my to do list.
It seems like gripes with PM companies have been a common theme lately. I think the business has pretty thin profit margins and they tend to take on too many units, which results in the quality going down. Even with that being the case though, if you hire someone to do a job that's only 80% as good as you can do it, you are still freeing up your time to focus on other things.
I think whatever you decide, you should look to delegate some tasks out to free yourself up.