I've been using the Keeper for about 3 cycles now. It takes some getting used to, but I think it is well worth it. Just returned from trip and didn't leave one "clue" behind at the in-laws.
Read all the info on the mentioned websites and what they send you with the Keeper. It was not hard to insert, but learning to take it out is a bear! Make sure you break the suction completely or it really hurts (voice of experience!) They say you can keep it inserted up to 12 hours; I have done that with no problem. When removed and emptied, they recommend either rinsing it out or just wiping it out . One woman said she carries a small water bottle with her to rinse it off in public restrooms.
I do have a little breakthrough on occasion; I've made little cotton reusable pads to use early on in my flow.
I think it's a great product given the convenience and no more trash!