Sorry, I know this thread was started a while ago, but I thought I'd share my experience.
KeraStraight was the second BKT I tried (the first had no result, can't remember which brand) and I was so happy with it - I live in the tropics (crazy humidity) so have always battled with frizz. The BKT took out the frizz from my 3a/b locks - I lost a bit of volume as well, but my curls were getting unruly so I can't say I was upset to let them go.
1) I couldn't let my hair air dry or the frizz would return - so I would have to blow-dry every day which was both time consuming and really bad for the ends. I had to get a separate moisturising treatment to repair them after the BKT wore off!
2) It wore off in less than a month. I suppose this is something to do with the humidity and the natural curl of my hair but obviously it is a very expensive treatment to get as a student to only last 4 weeks.
3) The shampoo/conditioner combo is very expensive and doesn't last too long (I exercise a lot so need to wash a lot) - it does smell lovely though.
I'd definitely recommend it - I'm going to get it done again soon, because I've heard that from the 2nd treatment onwards it starts staying in your hair longer. I wish it was a bit cheaper so I could justify it - but how great I felt during those first 3 weeks after the treatment probably is all the justification I need