Just submitted my biometrics a few hours ago in PA. Had booked an appointment for July 17, on July 14 through the buggy site -
https://my.uscis.gov/appointmentscheduler-appointment/ca/en
Showed up at the ASC 5 minutes before the appointment time, they asked me for three things -
1. ASC Appointment Confirmation Letter
2. Biometrics Letter
3. Passport
There were hardly 3 other people at the ASC. I went in and was done in about 10 minutes.
Came home and the IRCC portal had already updated with the biometrics info.
Good luck everyone!