I've got a multi-layer application that starts with the repository pattern for all data access and it returns IQueryable to the Services layer. The Services layer, which includes all of the business logic, returns IList to the Controllers (note: I'm using ASP.NET MVC for the UI layer). The benefit of returning IQueryable in the data access layer is that it allows my repositories to be extremely simple and the database queries to be deferred. However, I'm triggering the database queries in my services layer so that my unit tests is more reliable and I don't give flexibility to the Controllers to reshape my queries. However, I've recently encountered several situations where deferring the execution of queries down to the Controllers would have been significantly more performant because the Controllers had to do some projections on the data that was UI specific. Additionally, with the emergence of things like oData, I was starting to wonder if end points (e.g. web UI or web apis) should be working directly with IQueryable. What are your thoughts? Is it time to start returning IQueryable from the services layer to the UI layer? Or stick with IList?

This thread here: http://stackoverflow.com/questions/718624/to-return-iqueryablet-or-not-return-iqueryablet seems to vouch for returning IList to the UI layers, but I was wondering if things are changing because of new emerging technologies and techniques.