Replying to OP, yes I hate this especially! Before finding this website I had great difficulty finding a new drama that I felt I might enjoy. All the reviews on dramacrazy (which is where I have watched a majority of my dramas, behind Kimchidrama, Viki, and good ol' youtube), often mention they have only seen the first episode.
It helps, in a way - but can be really misleading. The only thing I want the first episode to do is to keep me entertained so I feel committed to watching more. How would Love Rain, Secret Garden, and City Hunter (to use my own experience) make sense if the review is based off the first episode alone??!?!?!??!