I was thinking about adding authorize.net's check option to my checkout. Do people ever use a check online, is it worth it?
It's not used very often in our observation. Typically the only time we see it widely used is specifically for businesses that require a check or ACH payment instead of a credit card. These are typically stuff like payments for loans or similar transactions where they don't want the customer to have a 6 month chargeback window but they are in a position where the customer is definitely going to pay them. You could test it, but I don't think most businesses will see a conversion increase just by adding an echeck option. Some might actually see a decrease if it makes the checkout process more complicated or confusing.