They're a ton of work, more so if you're not used to reading technical papers. It's also easy to get behind on the project, which is a very independent activity. Graduate students themselves usually only register for 2 courses a semester. That being said, if you make it through you'll be familiar with what is essentially state of the art. I'm finishing up the networking grad class this semester and I'm very pleased with it. Although I'm not exactly the best person to listen to when it comes to balancing work because I constantly overextend myself.