I stumbled upon the concept of menstrual cups last summer, pondered the "which cup"-question for about a month and went with the Keeper Moon cup - and am really happy with it!
As it turned out when I got back to school after the break, a bunch of girls in my co-op were already using cups, and I ordered mind together with another one who wasn't yet a cup-user. This was in August I think.
I had a really smooth transition, except for some sore muscles (I believe that's what it was) on my first period with the cup and a bit of leaking (oddly enough not until my third cycle with the cup). My friend had a bit of a harder time with her moon cup, and before that she had tried using a Diva and couldn't get it to work for her. But - as she told me yesterday - sheis now a very "happy camper" and completely bleached-cotton-free :)
To top of the story, I was one of the first people to sign up for the somewhat sketchy C'elle survey and actually received their package. The cup was exactly the same one as I was already using - and liking a lot -, so I decided instead of keeping it as a backup to pass it on to another housemate. She had originally been a little grossed out when we started talking about menstrual cups at the dinner table, but apparently got curious and is now going to try it out!
So all I can say is, even if on this forum a lot of the time people try to get solutions to their problems, cups really are awesome. If it doesn't work for you the first time around, keep trying.
And they are becoming more popular. At this point, at least 5 (and counting!) out of the ~15 girls (granted, all liberal college students, but still) in my coop are happy cup users :D