I have tried ACM-Server for my school and it is very cool.
I have a suggestion to make it better. Currently it is quite slow when I have more than 10 contestants because there is a bottleneck of using one judge id to submit the programs. So it will be better if we have multiple judge ids. It will be much faster since currently one judge id submits a program and wait for the feedback to submit another one. While with multiple ids, we can submit many programs with different ids.