I went at the end of my second year. I really enjoyed it, especially meeting other students and finding shared experiences. It broke up some of the PhD isolation I was feeling strongly at the time. The evenings were a lot of fun (going out to the pub etc), the mentors were supportive. We did an excercise where you do a mock application form for a job and then you do a mock interview and get feedback - that was quite valuable. It was also good to think about potential future goals and career plans and practice presentation skills. The only thing is its fairly intensive - I was expecting a bit of a holiday but no such luck! I would recommend it, unless you really hate meeting people and self-reflection (you do quite a lot of both).