I have a sitting desk currently. Standing desks are coming tho! I'd much prefer to stand a few hours a day even if it calls into question my sexuality.
Edit: I think a yoga ball would hurt my posture, not improve.
We banned stability balls due to safety concerns. The potential to fall off and OSHA's rights to a safe workplace that include a lot of ergonomics mumbo-jumbo. We looked into it with our comp broker and they sited several studies that find the majority of people who sit on those things eventually get fatigued and resort to "non-natural" postures (aka "slumping").