I just recently upgraded to BP 1.5 and I tried to turn off the BP admin bar and use the built in WP bar.
In WP-config.php I have:
// Uncomment to disable the site admin bar
//define( 'NOADMINBAR', 1 );
//define( 'BP_DISABLE_ADMIN_BAR', true );
define( 'BP_USE_WP_ADMIN_BAR', true );
When I do this I have some users reporting that when they login on the main site the "MySites"admin bar drop down doesn't appear for them.
What would cause that? They all have at least 1 blog. Do they need to have more than one blog for that menu item to appear in the admin bar?