I tried the yoga ball for a while too, after having back and shoulder problems from sitting at a desk all day. For the first while, it was alright...but once I got used to the instability, I found myself slouching, sitting in crappy positions, etc, and before long, I was back to where I started.
After dealing with a few months of near-unbearable lower back pain (that was eventually diagnosed as degenerative disc disease...at the ripe old age of 32) earlier this year, I stumbled across a bunch of standing desk info...and found a bunch of big books, old cd cases and a piece of melamine-covered particle board (from the cut-off bin at the hardware store for $2) and made myself the most ghetto standing desk imaginable. That was in June, and I've been standing happily ever since (I just gave'r and went for the full workday on day 1, no issues). And my back pain was gone within the first work week.
599946_10150912972675248_235607341_n.jpg Super ghetto.