abnormal uterine bleeding
"I loved this IUD.  I've had bad experiences with birth control pills (mood swings and acne) but this didn't cause either.  Ortho tri cyclin made me crazy and my acne went insane. Downside was it didn't help my endometriosis, I started getting ovarian cysts, and my boyfriend said he could feel it :(

Overall, I'm basing my rating on no initial side effects, plus my reason for using it was more special case (endo) and skyla can cause cysts in a percentage of people who take it, not everyone, and they go away once the IUD is gone. 

It would be excellent if you aren't in that percentage, are using it exclusively for birth control, and are dating someone that isn't big enough to feel it ;)"