I had one before we got married. I didn't have it in for the entire 3 years, just a bit over a year. I didn't have AF on it at all, didn't notice any change in libido. I got it removed as after about 6 months I started putting on weight, I really think it was more fluid retention as the extra kilos kind of just disappeared once it was gone.

I don't know anyone who has fallen pregnant on it and I know of quite a few people who have chosen this over iud or the pill. I'm pretty sure it is 99.9% effective, so if 1000 women use it one woman could possibly fall pregnant. As for the science behind it, the hormone is released slowly over the 3 year period, that's all I really know!

At least it is simple to try out and remove if it doesn't end up being right for you, good luck!