Being a fan of Dave Ramsey, I've come to use them rather than my checkbook or credit card. The newer cards, like my BoA Visa debit card is usable wherever Visa is accepted (i.e. nearly everywhere), it carries all the fraud protection of Visa credit cards, and it's no different than using my check book, just more convenient. It also gives me access to a huge network of ATMs.
Mark
One problem with debit cards for businesses is they are not protected against fraud.