DMV in the District had a pretty long line but was fine otherwise. The biggest problem I saw was people who had not read the provided information/required materials in advance of coming then started arguing or pleading their case.
You get problems when the employees cannot interpret the rules correctly, though. For example, proof of residency can be utility bill from the last 60 days, OR a DC property tax bill, and they reject a current DC property tax bill that wasn't issued in the last 60 days.