When should startup parameter -E be used?

Question

We are starting to build a data warehouse system using SQL Server 2008 R2. One of the senior DBAs told us to consider using a startup parameter -E for the SQL Server service. I read from Books Online that:

-E: Increases the number of extents that are allocated for each file in a filegroup. This option may be helpful for data warehouse applications that have a limited number of users running index or data scans. It should not be used in other applications because it might adversely affect performance. This option is not supported in 32-bit releases of SQL Server.

My question is how does this parameter help index and data scans? Should we use this parameter if there is a possibility that there are other databases (possibly in operative role) in the same instance?