Although my visa category is different I hope the review will help others in future.
There was a queue outside the embassy but most of them were for visitor visa. There was a separate line for immigrant visa but no one before us as our interview as at 9.30. Standard security procedure, only difference I found was that they did keep mobile phones in an open shelf and give a token to collect it during exit. No other electronic devices are allowed.
Inside, our originals were collected at the window. Within few minutes we and few other immigrant visa applicants were told to come back in the afternoon for the interview which as a bit surprising. Anyway, in the afternoon, only the immigrant visa holders were present so not many people inside. At our turn standard questions were asked. The computer system was out of order (upgrading to new system) so we were told leave all our originals behind along with passports.
For anyone who has any unmarried child (guess it applies to 18 plus age), please remember to fill two extra forms (selective service and marriageable act). The embassy forgot to ask my son to fill this form and they held our passports until these forms were signed by my son and received by the embassy.
The visa officer told us that we do not need the "famous" sealed envelopes anymore as the new system is now implemented. However, when we received our passports back, we did receive the sealed envelopes. Guess the new system is still not functional.