I had watched periodically, but really got hooked last year during The Year of Sue. My DS is a junior, so I was sucked right into Sue's college application journey.
I loved the episode on the plane when Sue was finishing her common application essay that goes to all the schools. They hit a turbulence bump and she accidentally hit send. Rereading it, she realized instead of ending with how she would "shoot for the stars", it ended with "shoot out the cars". Still makes me laugh!
My favorite episode is The Waiting Game. I have watched it 4 times and still have it saved on our DVR. Its the one where Sue is waiting to hear back on her college acceptances. Really a great episode that humorously looks at the stress of that whole process.
I enjoyed Sue's graduation episode, too, especially the part when her yearbook finally made it back to her.