I've always had great luck with the SC agents at DTW and they have gone out of their way several times for me. Last time I needed assistance was a couple weeks ago when there was a delay at EWR and the agent rebooked my non-status friend and I who were upgraded at the window into an LGA flight and kept our upgrades. I've also flown with non-status friends to Chicago or NYC and the diamond desk had told me that non diamonds couldn't coterminal and it is never an issue getting the DTW SC to do it. Whenever I've been concerned about a severly delayed flight cancelling they will put me on the next flight while protecting my seat on my ticketed flight in case that flight goes out earlier (I can never get the diamond desk to protect me on a second flight).

DTW is also great about keeping the main SC open late when there are flight delays. When I flew out of EWR earlier this year my flight was delayed by almost four hours and they didn't keep their SC open. The only SC I've really had bad luck with flight assistance at is FLL and BNA. The agent at FLL was clueless that as a diamond I could SDC from a FLL flight to Miami for free and insisted I could only do it from FLL