Menstrual cups: what's the deal?

Hi ladies, me and my friend have been considering using menstrual cups, in particular the lily cup from intimina. 
However I'm kind of frightened to use one because I don't even use tampons! 
What are your experiences on menstrual cups??
I've heard they can help with cramps which I get quite severely and tampons sometimes agitate my cramps when I've used them before so that's why I use pads.