I have had no bad side effects whatsoever with Armour Thyroid. I was diagnosed 6 years ago with Hashimoto's Thyroiditis (before I became symptomatic, actually, it was dumb luck that my neurologist sent me to the endocrinologist for a slightly off T4 level.)
I was started on Levoxyl (sp?) which gave me a headache every single day at the exact same time, exactly 9 hours after taking the pill. Then I was given Synthroid at too high a level and had rare side effects which subsided when I went down.
However, a couple years later I became symptomatic for Hashimoto's and although my endocrinologist swore up and down that no one should take Armour Thyroid, I had read otherwise, and had asked about it an an online women's forum. 9 out of 10 women on the forum said they did much better on the Armour Thyroid, and my new wholistic physician said, "Interesting, those are the same statistics I have in my office."
All my Hashimoto's symptoms went away within 6 months after starting Armour Thyroid and I've had no problems in years.