The new query system now interprets $all as syntactic sugar for $and. In some cases this can cause different query behavior in 2.5 compared to 2.4. See https://jira.mongodb.org/browse/SERVER-11785 for details.

The 2.4.8 documentation (http://docs.mongodb.org/manual/reference/operator/query/all/) says the following: "The $all operator selects the documents where the value of a field is an array that contains all the specified elements." This is not strictly true now that $all is shorthand for $and.