Some of the issues addresses by this library are the binding of the money amount to the currency, and currency conversion operations. If your code needs to deal with multiple currencies, you’ll definitely benefit from this library. But even if you are dealing with a single currency, it’s still pretty handy, making the code more transparent and future proof.
Martin Fowler has an excellent article on the “Products Over Projects” subject. It depicts the differences of both, with advantages and disadvantages, especially in areas like funding, team management, and iterations.
It’s a great read for anybody involved in software development, product and project management.