I used epoptes for almost a year. My impressions, so far:
1. Works great inside a cabled LAN, but in WiFi rooms, if a client gets disconnected, it won't reconnect without a server restart. There is a Brazilian fork, but it's too unstable.
2. Teachers hate it, (don't know why), the prefer to walk the classroom.
3. It's NOT in active development. Last update was in august 2012.
Frankly, after a year, i don't use it anymore. VNC, and a shared folder works pretty well, the only thing i miss is the ability to "silence" all the nets in the classroom.
THE class control software is the intel e-learning suite. It's awesome, specially the latest versions. But in Argentina the government purchased the windows version (FAIL), if you can afford it, don't doubt.