I feel like an impostor because I started out a 2b (and not very wavy at that, just frizzy and difficult to style), but this seems to be a great place for info on treatments.
Anyway... I've had two Kerastraight treatments now, about four months apart, both very successful. My hair was poker-straight for a short while after the first treatment, then just gradually settled down to straight-ish hair with a bit of movement, but that (miracle of miracles!) I could rough dry and look like I'd had a salon blow-dry. Even air-dry was looking reasonably good with no-frizz. After about four months it was just starting to wave a bit around my face where the new growth had come through, and it was feeling a bit straw-like at the back of my neck.
Since the second treatment I've been less diligent about the products I'm using (a cheap no-SLS shampoo instead of the KS one which I didn't like, although I am mostly still using the KS conditioner) and it seems to have made a difference - the poker-straight phase lasted no time at all, but I'm two months in and I'm still rough-drying and it's still looking pretty good. Air-drying gets mixed results, but still no frizz so I can live with a few unpredictable wavy bits.
I know everyone's hair is different so you might get a completely different result, but I'm absolutely going to keep using this unless something even better comes along. Only needing to rough-dry my hair is just amazing.