I have participated in a few Round Robins and the worst experience I had was when a Quilt I was working on went missing after I posted it, never to be found. I felt for the person who had made the first block and the two people before me who had contributed borders also. A word of warning always courier and get tracking on quilts sent, if this had been in the rules it would have made the tracing of the parcel a whole lot easier, as it was I felt guilty and the other people were frustrated.
However on the whole I have had quite positive experiences when doing R/R
3 lovely quilts and one not so good... an Amish type with a purple that faded into the black background used by a person that didn't step back to look at the colour choice
Anyways I say go for it you never know what you will get and you can learn new techniques and colour choices lots of surprises normall