I think you should talk to your doctor just to be sure everything is cool.
I spotted for six fun-filled months, but I stopped getting cramps as soon as I got it. I was bloated/fat when I got it so I didn't notice more bloating.
I don't remember if I had any bloating, but I spotted for 6 full weeks after I had Mirena put in. It was all worth it though because after that I didn't get my TOM until I had the IUD removed 4.5 years later!
I never had bloating, but had spotting for a long time. Even three years into it, I would spot for almost 2 weeks a month. It didn't bother me too much. But, I started noticing that 6 months into having the iud, I started to get mildly depressed. I thought it was because my mom died, but it lingered on. I just had no zest for life anymore and was really withdrawn from people. And angry at my kids all the time.
I finally figured out it was the mirena. I had it taken out a couple months ago & feel normal again. I don't think it's very common, but wanted to mention incase anyone reading this is also going through the same thing.
I never got bloated, but I did have cramps for a month or so after having it inserted, and I spotted off and on for months and months. It wasn't really a big deal - not even enough spotting to wear a pad or panty liner, just enough to see on the toilet paper. It's been about 1.5 years and now I get a light period every month with minor cramps. I had really nasty periods that would leave me homebound before Mirena, so it's a big improvement for me. I'd check with your doctor about the bloating though, to be sure.
I had spotting and bloating for a while after getting it. After that, for about 8-9 months, I'd get occasional spotting like a very light period. I've had it for just under 3 years and still get some bloating/cramping occasionally, but I haven't had a period (and only 2 episodes of spotting) since May 2009.