Forgive me for again directing you elsewhere, but I wrote on this just a couple days ago
http://sqlinthewild.co.za/index.php/2007/12/30/execution-plan-operations-joins/[/url]
Again, if you have more questions, I'll be very happy to answer them.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability