I've used the ION brand flat iron back in the middle of July and I actually loved the results (of course i had used chi shampoo, treatment, and silk infusion). When I went to the aveda salon to get it styled, the stylist used a chi and i got great results with that as well. However recently (like end of july, 2 weeks after my first attempt) i had a friend use the chi on me and i really didnt care too much for it. my ends looked damaged and my hair felt dry (i didnt use the chi produts then). so i think it has a lot to do with products first, then the iron.
Oh, i used my friend's sedu once and i hated it on my hair, it smelled like cooked bacon and it did not get my new growth at all. hope that helps.