Just how seriously alienation is viewed varies from judge to judge; only a relatively minimal amount of recognition has taken place at the official level, as reflected in State Statutes, where it is virtually non-existent.
Still, many courts do not consider evidence of alienation to be serious issue. If you intend to make evidence of parental alienation a factor in your case, be aware that in some venues you will have to mount an aggressive effort in order for the evidence to be heard.