I believe that the reason Disney did away with this is because of the simple reason that many parents were cheating the system. That is to say, a taller sibling would get measured, then the parents would switch the wristband to the shorter child. Obviously, that creates huge liability issues if something were to happen.
What I suggest if your child is "right around" but AT the height requirement for a ride (ie, they are 40" tall for a 40" tall height required ride):
1) Go early in the day -we are taller in the mornings than in the evenings/late in the day.
2) Make sure your child understands the importance of standing up straight -a lot of kids don't get this, or fool around a bit, but the CM's (who risk losing their jobs if they let a smaller child slip through) take this very seriously.
Also, keep in mind your child may get measured twice, once at the start of the line and once right before getting on. They have to stand up straight both times! Some parents practice this with their kids at home.
3) If your child rode an attraction one day, but then couldn't the next (or even the same day) try waiting for a bit, then getting back in the line. The CM's switch off, and one might measure differently then the next.
4) Leave the platform shoes, wild hairdo and stove-top hats at home. They aren't going to work.
5) Prepare your child BEFORE you go that there may be attractions they aren't tall enough to try.
