I do not see why CodeFirst can't be used in large enterprise projects. I will say that I use EF CodeFirst in several projects, one where the database is generated by my EF CodeFirst model and the 2nd where EF CodeFirst is mapped to an existing database.
From my experience, how effective CF is in a large project heavily depends on how abstracted your data layer is from your business layer.
For example, in one of my projects the business layer directly calls the database through linq. I use Linq to abstract away my database layer and use CodeFirst to map my POCOs into the database schema. In this case CodeFirst heavily makes the act of maintaining differences between DB conventions (relationship and table names) and my C# class names much simpler, and I can make database changes without having to heavily affect how my business layer interacts with the database.
However, in another project I have abstracted database access into a non-generic repository pattern, and my repository's Get* methods are solely responsible for running queries on the database, and they return real objects (not
IQueryable<T>s). In this instance, the repository methods are converting DB entities into the POCO entities and in this case CodeFirst doesn't provides as much benefit to you as the CodeFirst POCOs are short lived and are quickly converted into business layer C# classes.
Ultimately, it really depends on how the team is structured and how comfortable the team (or seniors are) with the non-DBA engineers modifying database schemas, and how much schema changes are going to affect your code structure. With CodeFirst mapped to an existing database, it is trivial for me to remap a property to a new column name without having to do a global rename of that property name, which is especially a factor when you are talking about a name that makes more sense for a database field rather than a C# property. It is also trivial for me to add code support for new database fields without having to completely remodel my C# entities (one of the reasons I left Linq-to-sql to EF CodeFirst from an existing database).