After reading through this thread I made the decision to renew my passport in person. I let it expire in 2020 and didn't bother to attempt to renew until a few months ago. About 7 weeks ago I gathered everything and wanted to renew but was put off by the times I was seeing on this thread.

In order to do anything in person you need an appointment. The appointments can be made online or on the phone. The phone agents are useless, worse than calling tech support or a foreign airline (there's at least a language barrier there that explains it, not so with these guys...)

The website says you can schedule up to ten days before your international travel plans, but the site only shows you 9 days out 99% of the time. You'll get false positive space everywhere. I tried to schedule in Atlanta for several days, checking at midnight, 2am, 4am, 6am, 8am, throughout the day. No changes. Never any open spots. A few other cities would say there were appointments but when you click through to the next page, you wouldn't get any times available. Basically, space opens up 10 days out, but the site only shows 9 days out, so it'll say there's space because there is on day 10, but it can't figure out how to show you day 10. I was finally able to snag a day 10 spot in New Orleans and when I called the agent, he was surprised because he couldn't see any day 10 spots anywhere.

The cost to the State Department is the same in person as it is via mail, the expedited rate. I had an 8:30am appointment, there were three windows open, but 6 actual windows. 4 people ahead of me. No one behind me. They checked my paperwork, collected the money, and I was out in under 15 minutes. There was no one behind me when I left. So clearly there's additional capacity they just aren't doing it.

I was able to pick up my new passport 3 hours later. When I arrived, shortly before noon, they weren't processing new people, just distributing that days passports. Only one window was open this time. Again, they have the capacity to do more they just aren't.

Why it would take months to get a renewal via mail is beyond me if I can go in person and get in same day...