Well, I did a little scouting, and it seems Mirena is plastic, so metal wouldn't be a worry with one (unlike the older IUDs).

The amount of hormone released is so small in comparison to other methods of BC, that headaches would be very unlikely from this device.

I think I'll go ahead with it. Success rates comparable to sterilization... that's pretty crazy! Plus this can be removed if I want to try to conceive at a later date .