I was referred to the hiring official about 2 weeks after applying on USAJOBS. I received an email telling me I had moved to the next stage of the process, which was an interview, one month after the vacancy closed.
The intervew was by phone and they said they would call me at my provided phone number on one of three days. No time range given, no offer to allow me to give a preferred date or time. So three days of sitting by the phone, trying to get ready to switch into interview at a moment's notice. Not exactly fun, but at least everyone else interviewing was suffering as well.
The interview was conducted by a senior supervisory attorney as well as an ALJ. Both were very pleasant, but the interview was a scripted set of questions, which didn't allow for building of rapport. They warned me at the start of the interview that it was scripted and not to take any silence as a bad sign--that they needed to make detailed notes. That was a great thing to know before starting.
They asked 5 questions total, some with multiple parts. Mostly scenario type questions--"Describe a time where you disagreed with a superior's decision. How did you address it?"
The entire interview lasted about 45 minutes, with a period for me to ask questions at the end. I did a little closing argument/summary of my skills and interest of the position, which they seemed to respond positively too.
Overall, not a bad experience for a phone interview (my least favorite). The warmth and enthusiasm of the interviewers was a major factor. A time frame of a few hours rather than THREE DAYS would make things a lot less stressful for future applicants.