I've been using this for just a few months. I still have trouble getting the position correct and need to use "backup" protection. When it is positioned right it works wonderful! I really like the security of over night use.
It is messy to insert and remove but its easy to get over. Public bathrooms are really akward but since you don't have to "change" it as often as other traditional products you can usually wait until a better time.
I do like the product and will continue to use it but do understand that its not for everyone.
Ever since I had my son I have gotten the WORSE cramps. I never use to get any. I finally tried this product & NO MORE CRAMPS!!!! My only guess is the over-drying and chemical exposing tampons were to blame. I don't dread 'that time of month' like I had been for almost a year when I got this- I breastfed but was not amoung the fortunate that lose their monthly flow by doing so ;-p This was the best almost $30 I've ever spent, and best part is by spending that $30 I've actually saved so much more money by not buying those icky chemical harboring disposables anymore ;-)
I've been using reusable cups for about 6 years now. I initially bought the Keeper, misplaced it one month, and bought the Diva. Which I have also misplaced, but it's ok because I found my Keeper back.
I think people's questions fall under two categories- what are these cups like in general, and then which cup is the best.
In general-
The cups are fantastic. They last for about 10 years, and only cost around $30. Compare that to other products, and you'll see the money piling up in front of you. I also love that I can stick it in and forget about it for 12 hours. Again, no other products can compete there.
Then there's the environmental benefits- less production required, less waste generated, no bleaching used...
Health benefits- no association with TSS, doesn't dry you out like tampons can, no exposure to dioxins...
The only problems I found were that it's a little tricky the first couple times you use the cups, and if you are having a heavy enough flow that you need to empty the cup during the day, it's a little awkward in a public bathroom. I like to use soap and water to wash mine in between uses, but I suppose you could carry some wet wipes so you wouldn't need to leave the stall with your cup.
Diva vs. Keeper-
The Keeper is made of gum rubber, the Diva cup is silicone. The Keeper is not good if you have latex allergies.
The cups vary a bit in shape and stem length. The Keeper has a longer stem. When I first bought it, I found this uncomfortable. I cut a bit off, and haven't had problems since. This link has a visual comparison chart of the different brands- just scroll about halfway down.
Since I've never had the two cups at the same time, I can't tell you which I actually prefer...
I have to confess, though the idea makes a lot of sense, I was a bit dubious about the Diva Cup. It seems to work ok but I think I might try the other size or a different type. I did a lot of research and asked a lot of questions on blogs and discussion boards -- for, oh, about three months.
It's pretty amazing as a concept - and it makes a lot of sense. It's definitely a lot less waste and takes up less space than boxes of tampons. I'm ready to return all my unopened boxes of tampons to the store!