Here is my experience:
Filed AOS through marriage to US citizen from a J1 visa (same-sex marriage). NYC filer, filed I-485, I-130, I-765, I-131
12/06/18: PD
01/17/19: Biometrics
05/29/19: Case is ready to be scheduled for an interview
07/17/19: Received Combo EAD + Advance parole card
12/16/19: Interview scheduled
12/23/19: Received interview notice in the mail
01/29/20: Interview at Federal Plaza.
01/30/20: I-485 and I-130 approved
01/31/20: Card was mailed
02/04/20: GC in hand
The interview lasted 10 minutes. The IO just asked each other's names, DOBs. parents' names, occupations, when I moved in in my husband's apartment and the last time I entered the US. Then he collected the documents I brought (bank statements, insurance beneficiaries, phone bills), had a look at the photo album, and then said the case needed review, and he handed in the (infamous) white sheet of paper. I was disappointed (since he didn't really asked us anything), but less than 30 minutes after we left the building I got a notification "new card is being produced". I guessed it was just a formality in my case.
Total time: 14 months. A long, at times frustrating process, but overall smooth.
One last info, for those in J1 visas: when I first entered the US, my visa stamp stated that I was subject to the two-year home residency requirement. When I renewed the visa two years later the new visa said I was not. When I applied for AOS, I went to a lawyer who recommended me to ask for an advisory opinion to the Department of State to clarify this. Turned out I was not subject (the first visa had a mistake, phew!), and after that everything went smoothly (the lawyer said I didn't need a lawyer, which I found it very nice and honest, so I ended up filing myself).
My advice: be patient and very organized. Do not call USCIS unless for some very serious matter. Their customer service is useless. My interview notice took a week to arrive, which I found it suspicious since all the other notices arrived within 4-5 days, I called them and said they had not sent it yet, but it was not true (the mail was late for other reasons).
Good luck to all!