I had one for 5 years and it was great. Hurt a lot when put in and for a couple of days after I felt like i was having the most terrible period pains. After that though - no periods for the full 5 years - bliss! Had it removed then because that's how long you're supposed to have them for.
I was told they don't normally give them to you if you were under 30 and hadn't had children - which was me at the time, but because of the problems i'd been having, they let me have one. I thought it may have ruined chances of conception in future, but am happy to report i'm now 9 weeks pregnant yay !
I'd certainly recommend the coil though - so much easier than having to worry about taking the pill, getting prescriptions, buying tampons - ah, happy days !
(make sure you stock up on strong painkillers before you have it inserted though - just in case - but it will only be for a couple of days, if that, so well worth it!).
Good luck ! xxxx