I've had instances where the showing agent changes the appointment so many times causing the homeowner so much confusion that I have had to intervene. Not to mention the times when the showing agent doesn't show up for an appointment and doesn't have the common courtesy to call CSS to cancel.
I've had situations where I was told a lockbox is on the door, but when the key is used, the homeowner is in the home (once exiting the shower with a towel around him). Shouldn't the instructions be to ring the bell before using the key?
I've also witnessed other agents screaming at the CSS reps for no apparent reason. As in every other life situation, if you treat people with respect and courtesy, they usually reciprocate.
To answer your question - I have been very satisfied with the services of CSS.