I also bought the Keratin Kits one off Amazon and overall, I'm very happy with it.
It does take a long time to do, especially if you've got long, thick hair like mine. Also, the fumes that come off it when you dry are really really strong. Makes your eyes water, so definitely open all the windows and don't put eye make up on beforehand. Don't do it if you're pregnant or have young children in the house. I think I'll dry mine outside next time actually. It doesn't contain formaldehyde, so it's considered safe. It does contain a lot of chemicals, but what doesn't?...
Last down side, is that it does make your hair a little greasier. I have to wash my hair a little more than before. Certainly a fair bit more in the first couple of weeks, but then it settles down a bit after that.....for me anyway.
Overall though, it's worth it. It used to take me over an hour to dry and straighten my hair. Now it's 5 minutes with the hairdryer, or nothing at all.
Also, I would add, it's more of a smoothing treatment as apposed to a straightening. It does take a fair bit of the curl/wave out, but not 100%, which was good for me, cos I would have to have flat, poker straight hair.