My friend Sumul turned me on to the stand-up workstation.  So far so good.  I find myself shifting my stance every few minutes as my knees start to ache but hopefully that will go away.  I bought this three joint platform from Amazon called the Comfylap.  It's working ok so far.  I like the fact that the joints snap to degree markers so you can be sure the left legs are at the exact same height as the right ones (and the right angles at each joint).  Only downside I'm encountering is the platform is not 100% fixed in place so there's a little bit of bounce every time I type.  I did a makeshift hack by propping some boxes below it but it doesn't eliminate the bounce all together.  Hopefully I get used to it over time.  Only other solution I can think of is to get a shelf or a single block of wood but then I lose the ability to adjust the platform should I find the current height uncomfortable.  We'll see if the claims of burning 50 more calories per hour versus sitting are true...