Some of the benefits of doing this are:
No more confusion between a quarter and a golden dollar. This means that one area of resistance to use the dollar coin is eliminated. Dollar coins have lower life cycle costs than paper one dollar bills.
It takes care of a major issue in trying to eliminate the 5 cent coin. (You could make the 5 cent coin form something other than nickel but it would have to get a new nick name). Without a 5 cent coin (aka, a nickel), do you round up or down to the nearst dime? Then what do you do with a quarter? Of you round to the nearest 5 cents, but you will need to exchange dimes and quaters to get to the correct amount. Without a five cent coin, you can't make change for a quarter.
Per $100 of coins, Half Dollars are cheaper to produce.
So even if we hold on to a 5 cent coin, using half versus quarter dollars will save money.