Is the ADO.NET Entity Framework known for generating poorly performing queries?

This question is inspired by the comment posted to the latest ServerFault blog post : > Are you guys still using LINQ to SQL? I know I can use SQL Server Profiler and/or the ToTraceString method to see the generated queries and analyze them myself. However, I am looking for opinions from **people with hands-on experience with administering databases accessed by applications utilizing the Entity Framework**. Are Entity Framework queries a common cause of performance problems? Can LINQ queries be optimized in such cases or is raw Transact-SQL the only solution?