That depends on your situation.
If you have a small app that only queries a Model in a specific way in one place, then you may be prematurely adding complexity. If however your use of model queries (including creates and updates) start to get reused, then Repositories are a must. Try not to duplicate code when querying your Models, as it makes making changes error prone.
The other use for the Repository pattern is to setup a data domain (Your domain is the modelling of data that does not necessarily match your database structure). You would then setup the Repositories the model your domain, which in turn queries your Models which model your database.
Hope that helps.