I'm also considering a metal sink in bathroom but wonder about upkeep as well.

Care & Cleaning instructions vary by finish, but our general cleaning guidelines recommend washing with a soft damp cloth and a neutral liquid soap like Dawn dishwashing detergent. Never use an abrasive cleaner, cleanser or disinfectant, which will alter the surface finish and will void the warranty. We also recommend a high quality clear carnauba paste wax be applied twice annually to preserve the life of any of our living finishes such as Chrome, Nickel, Matte Nickel, Burnished Nickel, Sovereign, Architectural Bronze, Carbon, and others.
For more details, please refer to our website at http://www.waterworks.com/assets/pdf/Care___Cleaning_Reference_Doc_8.2.12.pdf