i think they are ment if you have lots of quries ,
like i have a Stored procedure that gets all the listings between xx and yy for my tv guide.
and these hgave a few factors to it, day, time, week, etc .. instead of writing lots of queries i can write a Stored procedure that have the same query for all channels but set values for sections like
@Day = 1 (is monday)
and that value is used in the Stored procedure.
and helps if i want to add another field to the query (bring in) as i can add it to the stored procedure and it works on all the places it sbought in.
also performace i think is a bit better (service releated idea)... they look very simular to a Access query, except you use @value/pointer is declaired.