I had this done last summer, and I really liked it. My hair is normally about a 2b, and with the Coppola keratin treatment, I was about a 2a. I still had waves, just without the frizz. (I purposely got it to eliminate frizz and curliness with the humidity). Plus, I was able to either let it air-dry or simply blow it dry in no time - I didn't need a flat iron at all!!
My hair is usally thin, so I don't have a whole lot of it. The keratin really made it a lot easier to deal with in our summer humidity.
I had really nice beachy waves.
I would say that it lasted about 2 1/2 months, but I tend to wash it every day, so it may have lasted longer if I skipped the daily washes. Of course, it is definitely straighter for the initial month after you get it done. Then, it starts to wear off.
I had no permanent changes - my hair went back to the usual after about 3 months.
I think you might like it. Good luck!!