Mine took 20 mins max! And I got pictures and a dvd of the ultrasound. But I didn't do mine at a hospital. ...
The anatomy scan is to measure your baby. His legs, arms, head, chest, heart, etc. When I went for mine I thought it was going to be quick but it took over an hour to get all those measurements! And depending on the hospital, they might discuss the measurements with you right there but at mine they dont. They give them to your doctor to review at your next appointment
Just like every other ultrasound (well in Australia it is) but takes longer as they check everything possible such as brain development and all the insides and growth and such.. Then right at the end is when you find out the gender :-)