These are the journal articles sparking much of this flurry of panic about sitting and working:
[Lynch BM, Friedenreich CM, Winkler EA, Healy GN, Vallance JK, Eakin EG, Owen N. Associations of objectively assessed physical activity and sedentary time with biomarkers of breast cancer risk in postmenopausal women: findings from NHANES (2003-2006). Breast Cancer Res Treat. 2011 Nov;130(1):183-94.
Patel AV, Bernstein L, Deka A, Feigelson HS, Campbell PT, Gapstur SM, Colditz GA, Thun MJ. Leisure time spent sitting in relation to total mortality in a prospective cohort of US adults. Am J Epidemiol. 2010 Aug 15;172(4):419-29.]
...and yes, the general consensus is that sitting all day will increase the risk of early death -- however, periods of just 5 minutes each hour of walking and moving will substantially improve that risk profile. So yes, if you're standing around and moving for at least a portion of each hour, you reduce some of the risk.
I don't know how much good it does, but I also swapped out my seating situation -- when I -do- sit, I'm using a Balance Ball for my seated times, so my abdominal muscles, etc' are still being used.
Standing too much increases the risk of things like leg varicosity and, if knees are locked too much (which we tend to do if we get stressed), it can increase blood pressure -- so it seems like the best mix for those of us who are office-bound is a good balance between sitting and getting up and moving around, including standing-capable workstations and things like tablets.