I've been doing a sit/stand mix for a couple years. In fact - we've had this discussion in the past. The adjustable thing can be done on a budget. I actually ditched the setup (pictured in that other thread) and went back to a make-shift set up that works for me and is more stable. I like the flexibility of standing and sitting. The exercise ball aggravated an old back injury of mine - so I've laid off of it for a while.
nothing fancy - monitor on an old luggable Compaq. Laptop in front with keyboard beneath. So when standing I use laptop keys and trackpad. When seated - I just tilt the monitor down and use external keyboard and mouse. I need to raise up the monitor a bit - I'm tall, and it's too low at the moment.
Not as my main job. I moonlight at video production sometimes. I left FinalCut open as an easter egg teaser for thenewgreen because we're working on another project...