Christopher Caldwell thinks that the Bush brief amounts to "the most important substantive defense of affirmative action ever issued by a sitting president. If the Court accepts the president’s reasoning, it will have rescued affirmative action from what appeared to be a terminal constitutional illogic. More than that–it will have secured for this rickety program an indefinite constitutional legitimacy."
Quick response: read Josh Chafetz's analysis. By making up new standards of the importance of state interests, the brief manages to be rhetorically pro-"diversity" [i.e. racial diversity] while arguing neither for nor against the key claim: that diversity is a compelling state interest even in the absence of prior discrimination. Calling it an "entirely legitimate" interest is a kind of constitutional damning with faint praise. Caldwell has only noticed the praise.