SQLServerCentral just posted a SQL 2005 adoption survey. They surveryed 610 site users and the results are pretty interesting.
In my organization we currently use SQL 2000 for most of our production applications, but that said, we are also migrating toward 2005 with newer applications. Probably single bigest reason I've seen to favor 2005 over 2000 is ETL. I haven't seen alot of adoption for many of the new features such as CLR integration, XML and XQuery and even the Service Broker for that matter. Some that I would venture to guess is a result of developers using tried and true methods.