My cycle started on a Thursday, but I had to be at my internship that day and didn't want to use my cup for the first time outside of the house, so I tried my cup for the first time when I got home. Insertion was no problem whatsoever, no pain and no issues popping open. I left the cup in for maybe 6 hours before removing, and it was probably just below half full (my first day is the heaviest). I was a little worried about removal but had no trouble whatsoever! I used the cup for the rest of my cycle, even trying it overnight and while I went to the gym with no issues. I was really so excited at how well it worked.
My only "complaint" which isn't really that big of a complaint, is that the time I used my cup overnight I woke up and could kind of feel the cup. When I removed it, it was like my vaginal walls could relax. Not sure if it is because the cup is too large or too firm for me. I did get the Large Lunette, despite being younger than 30 and never having children, because I was concerned about capacity. However now after using it I know capacity will only be an issue on the first day of my cycle (all the other days when I emptied the cup it was less than a third or quarter full after 8-10 hours). I am considering buying a small Lunette or small Fleurcup in the future, if this feeling persists after a few more test cycles. Either way, I've been made into a believer!