What are the benefits of being a student representative for your course?

TL : DR - It doesn't take up much time and is worth it.

General:

You attend departmental and maybe faculty meetings, get an insight into what is going on to make your course happen. You can bring forward suggestions and (minor) grievances which you discuss and try to effect some change in what happens (hopefully for the better). You will also meet a lot of new people within your faculty/department or across the university you may not otherwise meet.

I was able to develop analytical and negotiating skills in the role and the style of having a "difficult discussion" with others (which will happen in beyond university at some point).

Personal:

The skills I developed helped because I wasn't practically developing them elsewhere (I volunteered and did societies etc). I also got the chance to meet and speak to the Vice-Chancellor and Deputy Vice-Chancellors. I was able to help give suggestions to a re-writing of my undergraduate degree which are still there nearly 10 years later. It also (oddly) brought me closer to a majority of the staff in my department and was able to chat to them in a much more informal way and when I saw them after university it made my relationship very positive, but I did benefit from a friendly, professional department.