The setting to enable/disable OMA Browse is actually set during ForestPrep. Exchange 2003 ForestPrep will no longer enable OMA Browse by default. Exchange 2003 ForestPrep/Reinstall will keep it enabled if it was already enabled. This means that OMA Browse WON’T be enabled when running ForestPrep to upgrade from Exchange 2000. You can find OMA Browse settings in ESM, under Global Settings -> Mobile Services -> Properties

Note: ActiveSync and AUTD remain unchanged.