My reservations were:
I fell for the endo scare until I saw it debunked here.
I have an overactive bladder before and during my period so I was afraid anything extra inside would just put more pressure on my bladder and make me pee my pants.
I had thought the cup had to seal around the cervix which would probably be impossible for me. My canal is really wide at the top and my cervix angles back so that it's almost horizontal - the opening is flush against the back wall of my vagina when my cervix is high. (I also have a U shaped uteus, which I think is very cool, but that's probably beside the point.)
I have a long vagina, but I ordered a med. MeLuna because it seemed like it would be short enough to fit low and create a seal where my vagina is narrower. It arrived yesterday (a day too late to actually use it) and I popped it right in! It was sealed and comfortable in a matter of seconds. Very tight seal. I don't think it's going to leak. So, now I just have to wait until next month and see if it makes me pee my pants when I have my period! It fits low enough that I think it will be ok though.
And that's my story so far.
Thanks for all the info here!