US Tourist Visa - Appointment Processing Times

Just on my own recent experience of this - applied in January and was quoted an appointment of October. Ended up getting an appointment for September due to a cancellation. Arrived for my 8:15am appointment at 8am, where we were treated like drunken punters in the queue for the nightclub. I had a laptop in my bag and was told to come back next year with a new appointment unless I could drop off my laptop somewhere and be back within 15 minutes of my appointment. I just managed to do this as I work around the corner, no problem with the rules/need to be thorough, but the pleasure taken in telling me to get lost had me taken aback. On getting in to the security check point they were also very rude and actively intimidating - fair enough they have to be strict, and perhaps some of it is tactic, but I really wasn't expecting it. Consular officers were pleasant once inside the building itself. For anyone going for an appointment, have your ducks in a row going there, be early, and don't bring anything more than you need e.g. bags/electronics etc. it is airport level security.

Does anyone know how long it takes for passports to be returned via DPD courier from them? They state 2-3 weeks when applying but curious if this is overstated to allow for times when it is busy?