I had one with my last pregnancy at 23wks, could have been later but I couldn't hold off, hehe. It cost $140 and we got back $80 from medicare. With that we got 1/2hr video and 42 pictures on a CD-R.
They are pretty awsome, my Mil looked really uninterested and actually walked out of the room watching our 19wk scan.
So we had the scan around her birthday a week after I think and took her with us. She even commented that bubs had his daddy's nose, lmao.
I would get one done, it's a great memory to keep.