After experimenting with standing desks for a while I have noticed the following (YMMV):
1) You should ease into it - go from one hour to two in a week, two to three in a couple of weeks
2) GET Anti-Fatigue MATS to stand on otherwise sustained standing is going to Screw-up your legs
3) Have a stand-by(!) sitting desk and alternate between the two once you "get tired" standing
4) Don't be afraid to say "This does not work for me".
A colleague who tried it with me hated to say this, but she was in constant knee pain standing up but would not go back to her sitting desk.
1) You should ease into it - go from one hour to two in a week, two to three in a couple of weeks
2) GET Anti-Fatigue MATS to stand on otherwise sustained standing is going to Screw-up your legs
3) Have a stand-by(!) sitting desk and alternate between the two once you "get tired" standing
4) Don't be afraid to say "This does not work for me". A colleague who tried it with me hated to say this, but she was in constant knee pain standing up but would not go back to her sitting desk.