1. On the following page:
http://docs.mongodb.org/manual/core/query-plans/#index-filters

we discuss how Index Filters work, including how to remove filters, however there is no mention and links to how to create them with planCacheSetFilter

2. On the planCacheSetFilter page:
http://docs.mongodb.org/manual/reference/command/planCacheSetFilter/

it is fine to give a simple example, however, we should add a more complex example that uses a sort and a projection clause.