The investigator herself uses the system in real contexts and evaluates it. So, the investigator is the only “participant” in the field study.
No need to recruit participants.
A lightweight way to ensure that basic faults are corrected before a more expensive field study with users.
Hard to get real experiential data, this method rather finding "experience bugs" (and technical/usability bugs), than about subjective experiences.
Jordan, P. (2003) Designing Pleasurable Products
References describing the method