I have a similar issue using API express. Link to my original post: https://getsatisfaction.com/apperyio/...
basically i've add &sort=created_at at the end of my REST url request, however nothing happens.
I have also tested it and I can get it to work correctly for imported database services, but I can not get it to work for API express services as the two images below show
Trying various different fields and with and without the '-' I was not able to get the results to change in any way with a sort parameter.
This one worked no problems