I had the Coppola Keratin Express Blowout Treatment. I went with that one because my hairdresser told me it would only last 6-8 weeks and that why I could decide if I like it or not. Well I didn't and here's why to answer a few of the questions you asked.
2. Is it permanent? I got the express treatment the first week of April 2012 and it's still in my hair. It's warn off, but it has left my 3b curls as limp waves with more frizz than I had before I got the treatment.
3. Does it straighten your hair completely or can you choose how you want it to look? My hair was bone straight with hardly any body. It was however frizz free for the first 3 weeks which was nice, but it didn't last. With the return of the frizz, a slight wave started to return about 6 weeks later. And now, 20 weeks later I have a combo of straight pieces, limp waves, and some curls that resemble my old S curls...I miss those pretty S curls!
4. Does Keratin damage your hair? Although my hair lacks body now, it doesn't appear damaged from the treatment.
5. Do Keratin conditioning treatments (like shampoos/conditioners with keratin as an ingredient) give you the same results as the ones you get in a salon? I have never tried the home treatments either
If you do get it done, I would have your hairdresser do what Ninadef did and only have them run the flat iron through 5 or less times. My hairdresser did it 8 to 12 times and I think that's part of the reason why I completely lost my curl and body.
The good news is, I've been doing lots of TLC on my tresses and they are slowly but surely coming back to life! Good luck with what you decide.