Well the new 1$ coin addresses every issue with respect to telling them apart from other US coins.

The only other reason I can figure, is that merchants don't like them is because of how heavy they are compared to a stack of bills. Think of carrying a couple hundred in ones around when they are coins.

I'm really begenning to believe that the only way the 1$ coin is going to be widely adopted is if the 1$ bill is just taken out of print and circulation.