I have noticed though that $push only accepts a single argument. There could be plenty of scenarios where it would be useful to add multiple values at once to the array. The same would go with a $pull modifier (see http://jira.mongodb.org/browse/SERVER-130).

For example:

db.group.insert({_id:1,text:'user group 1',users:[1,2,3]});

// add some users
db.group.update({_id:1},{ $pushAll :

{ users : [4,5] }

} );

// remove some users
db.group.update({_id:1},{ $pullAll :

{ users : [1,4] }

});