I did this on our last trip on our date night. It was really fun, but not something I would do everytime. We went late in the evening and the person before me got the biggest pearl of the day 9 mm. I got the second biggest of the day! 8.5mm! I had mine set in a necklace charm that has two leaves on it. It was kind of unique, I thought. I have yet to take it out of the box (8 months later!). Also, mine was slightly pink.
When we went to pick up my setting there was a set of twins girls, about 12, and they each got a clam. Both of them got doubles! That was fun to see!