Good, Bad or Indifferent: WHERE 1=1
The SQL Server parser optimizer has a feature called "Constant Folding" that eliminates tautological expressions from the query.
If you look at the execution plan, nowhere in the predicates you will see that expression appear. This implies that constant folding is performed anyway at compile time for this and other reasons and it has no effect on query performance.

See Constant Folding and Expression Evaluation During Cardinality Estimation for more info.