OS Commerce
Overall quite easy to setup.
Cube Cart
Cons : Although price can be shown in any currency, but during setup or adding products, the price entered must be in USD. Then the system will use the conversion to display the desired currency. So for non USD based businesses, you will have to convert your pricing to USD and then let the system convert the price back. Therefore you may always get a price that has rounding values ie. $23.43 instead of just $23.40
Can setup your main currency as 1.00 in currency setting.
Cannot use my own payment gateway, ie. setup a link for payment.
Zen Cart