What are the “exceptions” for AOS in the US now?

If you have no issues, the regulations state that you are to be approved. If negative issues arise, they need to be counterbalanced with positive ones. USCIS officers have always had discretion.

USCIS has not yet provided a clear definition of what it considers “extraordinary circumstances” for Adjustment of Status (AOS) cases. The new policy memorandum emphasizes that AOS is a discretionary benefit rather than an automatic right and that officers should more carefully review each applicant's overall circumstances. However, the law itself has not changed. Congress still allows eligible individuals to apply for AOS inside the U.S., including many employment-based, family-based, and EB-5 cases. USCIS cannot eliminate those statutory pathways through a policy memo alone.
We are yet to see how aggressively USCIS will actually apply this guidance in practice. We do expect increased scrutiny, additional requests for evidence, and more focus on applicants’ immigration history, status maintenance, and overall discretionary factors. There is also widespread expectation that significant litigation will challenge parts of this policy if USCIS attempts to apply it too broadly or in a manner inconsistent with the immigration laws passed by Congress.