Most people know about the woes of commercial software, but let's recap quickly.
You have to trek out to a store or call up some vendor. You pay a hefty price up front, usually without ever having seen the product in action, plus most of the money goes toward defraying the company's advertising or other overhead costs. You seldom have money-back guarantees, even if the software is completely inappropriate for your needs or if you just plain hate it. You supposedly get professional customer support, which often means being on hold for half an hour just to talk to some technician who had nothing to do with writing the program. It's not always so bad, and in fact some products are really well supported, but you get my point.