SQL Server 2005 has reduced application downtime, increased scalability and performance, and tight yet flexible security controls.
SQL Server 2005 makes it simpler and easier to deploy, manage, and optimize enterprise data and analytical applications.
It enables you to monitor, manage, and tune all of the databases in the effective way.
Failure of the primary system, applications can immediately reconnect to the database on the secondary server using Database Mirroring.
SQL Server 2005 provides a new capability for the partitioning of tables across filegroups in a database.
Has Features of XML, Multidimensional Expressions (MDX), and XML for Analysis (XMLA). Integration with the Visual Studio development environment provides more efficient development and debugging of line-of-business and business intelligence (BI) applications
SQL Server 2005 provides a lot of benefits over SQL Server 2000 including within the replication feature set.
You might be relieved to know that, although most of the benefits accrue on the side of a SQL Server 2005 Publisher, you can still set up SQL Server 2005 as a subscriber on a SQL Server 2000 Publisher. Thus, you can begin to merge in the newest release of SQL Server into an existing replication scheme. You can read more about this here.
Although major advantage to SQL Server 2005 over 2000 is that changes to the schema, such as through ALTER TABLE statements, replicate out to all subscribing servers. The cool news in a mixed version environment is that the ALTER TABLE statements will be published to SQL Server 2000 Subscribers from a SQL Server 2005 Publisher.