Hi Embracethechaos,
The actually fitting is about the same level of pain and discomfort as a smear test, so if you've had one of those you'll know what you're in for. If you decide to have one fitted, ask around to try to find a professional who has a lot of experience fitting them. I had mine fitted by a GP who was experienced in fitting them, but I have heard that a sexual health clinic can be a good option too.
For me the pros are that it is reliable (no pills to forget, lasts for 5-10 years depending on the coil, and the failure rate is tiny) and it was important to me not to take hormonal contraception for a few reasons.
The cons are that the copper coil can make periods heavier and more painful. I never had menstrual cramps before I had mine fitted and afterwards the cramps only lasted one day each cycle but they were disabling if I didn't have ibuprofen to hand. The cramps are worst in the first year after fitting and then they settle down (no idea how that works). I've actually had two copper coils, one for five years and then another one for another five years. When I had the first one fitted my periods also got longer by one day, and that has stayed the case. They were always quite heavy and I am quite anaemia-prone so that isn't great. The other con is that there is a risk that, if you do get pregnant on the copper coil, the probability of the pregnancy being ectopic is higher than in normal pregnancy. Therefore it is good to know the symptoms of ectopic pregnancy if you have a copper coil. The absolute risk of it happening is tiny, but ectopic pregnancy is quite dangerous I think.
There is the option of a coil that contains hormones which can make your periods lighter or even stop completely but I didn't want that, I prefer the copper one. Overall I am very happy with my choice.
Hope that helps!