At my height, bar tables are perfect standing desks, and bar stools are perfect if you want to sit down without having to think about changing desk height.
Wouldn't it be awkward over long hours though? Specifically wouldn't you want the keyboard near your waist and the monitor closer to your head, as opposed to bending to look at the screen; or having to raise your arms closer to your shoulders?
The keyboard is ~6 inches above my waistline, which feels perfect to me. The screens are the same distance from my head whether I'm standing or sitting.
I keep a barstool by the desk for any periods when I am tired, although interestingly enough, I find that I sit when I'm learning, and stand when I'm producing (I'm a web dev). So exhaustion isn't the primary dictator of whether I'm standing or sitting.