The basic PSI customer service (the one you use to schedule and the one the testing center calls when they have problems) is indeed atrocious. I had them schedule me for tests at the local A&P school (they were the closest testing center), except that I was scheduled for a week when they weren't open for doing those tests. I ended up having a nice chat with the owner of the school and listening to him gripe about the fact that they told PSI that they weren't open that week... hell it was between Christmas and New Years so I understand, but still.
Then when I came back for the rescheduled tests, the system was farked up and wouldn't come up. The problem is I scheduled from as soon as the school opened, like 8AM eastern time. PSI support is in California and they didn't open for a couple of hours. They let me munch down on coffee and donuts in the staff lounge while I waited.
On the other hand, when the FCC wouldn't take a test PSI administered for me, I was able to escalate at PSI to someone who had a hotline into the FCC (I was getting nowhere with them) to get my licenses issued.
I expect things to only get worse now that the FAA has given them a monopoly on the things.