RP is the only realistic way to manufacture some of the parts. See Sandia Lab's web site for more information. RP may be used to build parts in space or on other planets. In existence for just 13 years, RP is still in its infancy. As a result, some limitations exist within RP, such as Size envelopes.
Larger parts can be quite expensive.
Limited material properties. Many argue that RP doesn't equal or rival injected molded parts. Because parts are built in sections, the properties may not be very isotropic. Surface finishes that require subsequent finishing labor. This is due in part to the accuracies of the technologies and can sometimes be caused by using too coarse an STL file.