I had achilles lengthening about ten years ago... I had regular casts, up to the knee. The doctor said that particular surgery would not be painful, but to be honest I found it VERY painful, a lot more so than the hamstring surgery, which I just had...but I was about nine then so that might've been a factor (over-reacting and everything

).
I was very weak after I got the casts off, but regained my strength with therapy. And it definately did help me to walk "correctly", instead of on my toes.