I'm three (now five, it's Friday!) days into my first cycle using the DivaCup. I was really excited about it and have had no problems, except my mom (who is a medical assistant) is concerned about it.
Basically, she's concerned that it "keeps the blood inside" me and that (since I can't fold it up while taking it out) the rim might be scraping the wall of my vagina and ... cause something bad. She's also uneasy about it being "plastic", and hasn't been reassured by the repeated "vulcanized, medical-grade silicone" explanation.
As to the first count, I read a lot of stuff in the memories about retrograde flow, but I don't actually think that's what she means by "keeping the blood inside" -- I think it's more that it doesn't get to leave my body for a few hours as it's blocked by the cup.
And as to the second, I do try to be gentle when I take it out, but it is still a little uncomfortable (although not in a way I can't just get used to).
Before you ask, my mom has a really negative opinion of tampons (although she does say she thinks the DivaCup is probably better than tampons) -- she and my sister (and me, up until recently!) only ever really use disposable pads.