They really are cool coins, about the size of the current US dime, and I have heard of people getting them in circulation as a dime. Here is an uncirculated example from 1865:
(http://www.scottishmoney.net/usa/3cent1865.jpg)
These coins were not overly popular in circulation even then, but they and the 2 cent coins stayed in circulation until ca 1900 or so when they started getting saved.
Curiously stamps are also the reason this thang was created - so people could buy 100 stamps:
(http://www.scottishmoney.net/usa/three1878.jpg)
The $3 coins were never really popular - but there were exceptions, they were popular in some mining areas for a particular reason - $3 represented the price of a night of pleasure.