I am scheduled to have Mirena put in next month. I've talked to friends, as well as my OB who has had it between both kids, and they all love it. Paragard seems fine too but I know more people with Mirena and they all have good things to say so I'm leaning that way.
We do plan on having another LO - but not for a few years - so it seems like the best option for us. I like the idea that as soon as we want to start trying I can have it removed and try right away, whereas the pill they recommend being off it a few months, plus there's always the issue of waiting for your cycle to get back on track. I was on the pill for like 10 years, which was fine, but with two kids I would rather not have to worry about taking it every day, getting it filled each month, etc.
As far as complications, there are side effects with anything you do so I think that all balances out.
Good luck with whatever you choose!