I had one, it was ok. I didn't love it, but it served its purpose. It didn't leak, and I couldn't feel it. Getting it out was a pain. I couldn't ever do it without a major mess (and I had the thing for 3 years). Sometimes it would cause cramping, but nothing major.
Then I lost it. I packed it for a trip, and never saw it again, I looked EVERYWHERE.
About a year of just pads, and sometimes tampons, I got sick of dealing with those, I was about to buy another Diva. Then I remembered the Instead Softcups, and decided to give them a try.
They are disposable, you're technically supposed to use it once and toss it, but no one actually does that. I wash and reuse for one cycle. They have all the conveniences of the diva cup (wear it for 12 hours, can't feel it, doesn't dry you out), but are much easier to remove and insert, and they're cheap, about $7 for a box of 14. That lasts a year! Still messy to remove (maybe I'm just uncoordinated), but there's a trick to emptying it without removing it (if you have heavy days). You can bear down and get it to empty, then it slides back into place, and and hands stay clean. Takes some practice, but it does work.