Addicting? That depends who you ask. My friends here at MIT who were on robotics teams in high school understand why I frequent it, those who don't (like my roommate) don't really understand.
I mean, I do spend a lot of time on Chief Delphi, especially during build season, but I also get good grades, do lots of extracurriculars, have friends and a social life, and (occasionally) sleep.
If I need to do other things, I will, but I will admit I'm hooked.