I have not encountered any stability issues with Microsoft Entra External ID.
Microsoft Entra External ID offers quick setup, generating unique IDs and keys in under 30 minutes, monitoring guest applications, and adjusting permissions. Seamless integration within the Microsoft ecosystem is beneficial, while firewall capabilities enhance security. Single sign-on access provides a secure environment. However, technical support needs improvement, and pricing complexity, high costs for medium-sized businesses, and inconsistent customer support quality are concerns, especially in some regions.