In many ways SQL Server itself is an EAV system. Tables, columns, constraints, they're all records in tables.

However, having said that, why reinvent the wheel? SQL Server actually abstracts EAV so we don't have to worry about all the (myriad) implementation details for a complex EAV system. I can live with that!

The one use case I have no trouble allowing in a model is that of "minor" tables, such as a 3-4 item list that would otherwise be hardcoded into the application and merely stored with a check constraint in a byte field.

One example would be a status field that basically said: Active, Inactive, Parted Out, or Destroyed. If you have a dozen such small status fields an EAV approach of key, value, and (perhaps) user explanation fields isn't burdensome.

Beyond that--well, too much work. 😀