On the positive side, Beneatha truly believes in her own abilities to achieve in areas of education, marriage, and life in general.
More neutrally, she is willing to completely break from the values of her family, as a free-thinker (religiously speaking) and as a person identifying with her African roots.
On the negative side, Beneatha is thoroughly embittered by the aspects of her life which represent the historic and arbitrary constraints placed upon her prospects. Her reactionary attitude shows itself in her treatment of Walter and Mama where she shows only belated affection and concern.
She is probably my favorite character in the play and represents, to me, a larger set of social choices for people who find themselves in a middle ground, intellectually and emotionally. Everyone else has a more binary set of challenges in the play. Beneatha's choices are somewhat more complex and probably best match those of the author.
To critique Beneatha's attitude means to critique her feelings toward and position on things, ideas, or people. Her name might give a clue about her feelings about other people, especially her traditional family and boyfriend: her attitude (feeling) is that they are beneath her. As she she gains a college education and becomes indoctrinated by Asagai, she finds less and less to admire in or be grateful for in her family. Her attitude (position) toward the African American identity movement is in large part fashioned by Asagai's pressure to conform to his standard.
Beneatha is torn between two worlds, and she is clearly uncomfortable in both of them. She has an attitude of entitlement as she plows through one activity after another before meeting Asagai. These are expensive experiments, costing her family money they can ill afford, and none of them has filled the void she is obviously trying to fill. After she meets Asagai, she is absorbed with native dress, music, and hair. These are also experiments; and as the family moves and refocuses its energies, she is likely to drop these interests, as well. Beneatha is both egocentric (focused on herself) and unfocused.
Beneatha's world, both inside and outside her home, has been turned upside down at the exact time when a young woman usually would be declaring her independence, seeking her own identity, and finding her way in the world. Her father has died, her family suddenly has money to spend, and she also is coming of age at a time of social upheaval. All of these circumstances make Beneatha's life and transition into adulthood especially complex. Is she the little sister who still chafes under her brother's domination? Is she her mother's child bound by love but struggling to become her own woman? Is she a talented young woman who dreams of a previously impossible life? Is she a young black woman who tries to find her identity and her place in an emerging social order? Beneatha is all of these, of course. Throughout the play, she is pulled in one direction and then another and struggles with conflicting emotions, even though she often masks her emotional turmoil with "attitude."
I think when we consider the character of Beneatha it is clear that she is a character with a number of tensions, as other posts have established. She has dreams that were unthinkable for her mother just a generation before her and yet at the same time she also seeks to return to her African roots, not looking to deny her heritage but to acknowledge it in displays such as how she wears her hair. She seems at times a bit bewildered by the freedom she has inherited, and in the play I think we see her struggling to try and find her identity and her voice.
If by critique you mean evaluation, then I think you could also add that Beneatha represents the NEW possibilities for young black women at the time period of the setting of the play, the late 1950's. She has dreams that her own mother never could have imagined having in her youth. She represents the black people who both embraced their ethnicity (wearing her hair naturally) and their new found opportunities (her thoughts of going to college to become a doctor!).
I think that if one were to criticize Beneatha, it would have to reside in her use of freedom. Beneatha represents that while freedom is wonderful to possess and something that has to be valued, it is best seen when it is channeled towards a socially redemptive end. Beneatha's voice is being explored with a multiplicity of vocality and a divergence that represents what it means to be young. Yet, in the end, she can be criticized because her freedom extends to only her and little else. She does not see herself as connected to the family, a unit that sacrifices for her and helps to allow her the freedom she so treasures. Criticism can be levied against her here. When the opening scene reflects the discussion of the insurance money and what happens to it, Beneatha lays claim to it, as well. This can be criticized because she is not making much in way of sacrifice for others and this self interest is what ends up being a part of her character. At the same time, another critique that can be offered towards her is that she struggles with finding her voice. Despite the fact that she possesses a great deal of freedom and autonomy, she cannot seem to channel it into happiness or some type of consciousness that will allow her to find some solid ground upon which to build a life. This is something that becomes a part of her character throughout the drama, reflected in her relationships with men and family members.