Using computed columns in SQL Server

In a database we need some values that were often calculated while generating several reports.

Assuming we have the following table:

CREATE TABLE InvoiceLine
AS
(
       InvoiceLineID int
       , InvoiceID int
       , NumberOfItems int
       , Amount money
)

And we want to find the total amount of an invoice line. We can achieve this by addding a new computed column:

CREATE TABLE InvoiceLine
AS
(
       InvoiceLineID int
       , InvoiceID int
       , NumberOfItems int
       , Amount money
       , TotalAmount AS (Amount*NumberOfItems) PERSISTED
)

Is this useful?