Greenberg and Buxton argue that the HCI community has overemphasized experimental evaluation, using it even when it is premature, and when it might be used well, using "weak science" that demonstrates a design's value only in the best case.
Greenberg, S., & Buxton, B. (2008, April). Usability evaluation considered harmful (some of the time). In Proceedings of the SIGCHI conference on Human factors in computing systems (pp. 111-120). ACM.