Within the academic literature for personality psychology, the Myers-Briggs Type Indicator (MBTI) is obsolete; the Big Five has been the dominant framework for studies on human personality since about 1990. The most-cited review of the MBTI was very critical of it (McCrae and Costa, 1989) (side-note: there is a conflict of interest in that McCrae and Costa receive royalties from their NEO-PI inventory of the Big Five). Here is the abstract:

The Myers-Briggs Type Indicator (MBTI; Myers & McCaulley, 1985) was evaluated from the perspectives of Jung's theory of psychological types and the five-factor model of personality as measured by self-reports and peer ratings on the NEO Personality Inventory (NEO-PI; Costa & McCrae, 1985b). Data were provided by 267 men and 201 women ages 19 to 93. Consistent with earlier research and evaluations, there was no support for the view that the MBTI measures truly dichotomous preferences or qualitatively distinct types; instead, the instrument measures four relatively independent dimensions. The interpretation of the Judging-Perceiving index was also called into question. The data suggest that Jung's theory is either incorrect or inadequately operationalized by the MBTI and cannot provide a sound basis for interpreting it. However, correlational analyses showed that the four MBTI indices did measure aspects of four of the five major dimensions of normal personality. The five-factor model provides an alternative basis for interpreting MBTI findings within a broader, more commonly shared conceptual framework.

This was interesting (italics mine):

Most conspicuous is the lack of a Neuroticism factor in the MBTI. Its absence is understandable on two counts: first, because emotional instability versus adjustment did not enter into Jung's definitions of the types, and second, because the authors of the test were apparently philosophically committed to a position which saw each type as equally valuable and positive (Myers with Myers, 1980)—a view that is difficult to hold with regard to Neuroticism. (To a lesser extent, the same criticism applies to the TF and JP indices. Descriptions downplay the antagonistic side of Thinking types and the lazy and disorganized side of Perceiving types.) Although it makes interpretation of results palatable to most respondents, this approach also omits information that may be crucial to employers, co-workers, counselors, and the individuals themselves. For many, if not most, applications, some measure of Neuroticism would be useful.

e.g. if I'm asked if I'm extroverted what baseline am I comparing myself to?

I took an online Big Five personality test, and it explicitly said I was to compare myself to typical people of the same gender and age as me (which, since there are huge selection effects in the kinds of male twentysomethings I hang around with, meant that in lots of questions I wanted to answer “how the hell should I know?”).

What do people think of the Myer-briggs personality system?

Astrology for geeks.