The first and foremost problem with a white box laptop has to do with warranties. When a complete laptop is purchased from a tier one manufacturer, it comes complete with a warranty for service for any parts that reside in it. White box laptops are much more complicated. If the system was put together by a store, they may offer a warranty, but they are more than likely to require that each part be warrantied from the manufacturer. This can make things complicated if a part breaks and needs repair.
Another advantage to a white box laptop is its upgrade potential. Most laptops now sold by the major companies are sealed such that only a few parts such as memory can be upgraded. With a white box laptop, the majority of the parts are easily accessible because it has to be in order for the components to be installed in the first place. This allows users to upgrade optical drives and processors without having to go through a manufacturer or buying a new system. Only the smallest ultraportable chassis tend to lack the widest range of upgrade options.
Another thing that many white box laptops lack is software. It is up to the consumer generally to supply all the software. This may not be a problem, but many tier one manufacturers include that can save a lot of money but they can also install a lot of unwanted software as well.
White box laptops are definitely a much more viable option than they were even a year or two ago. For the majority of users, a white box laptop is likely to cause more issues for them than if they were to buy a major name laptop. The people who benefit the most from the white box laptop are those looking for specific features in a mobile computer that no major manufacturer supports or those who are already quite familiar with computer hardware such as desktop computers.