Well I joined last year when I came to Mac Uni - you stay part of the program for at least 3 years.
This year the only events were a formal introduction - good for meeting people outside your degree area and a 3 day aspiring professionals workshop held at a college on campus. This was a great time about teamwork skills, what to get out of uni, advice from successful people, etc. From that I am now friends with a great deal of people - see more familar faces around uni.
The organiser does contact you guys about offers at uni like job chances as well.
So it was good but just not much of it.
But it does give you something extra on your CV and you could make some good friends too.