A big hooray! We've migrated our production environment to SQL Server 2005 today!
Tomorrow will be a first test day but Wednesday will be the real test since most offices are closed tomorrow and Tuesday making Wednesday a little heavier too :-)
A couple of figures:
Database Size: 330GB
Daily growth: 2GB
Max. Users: 4500
Concurrent Users: 2000
So far it is a 'flat' migration meaning we haven't implemented any new features and will keep it this way for another 2 weeks to make sure everything runs smoothly. We have a transactional replication to SQL Server 2000 so we can go back whenever something goes seriously wrong. After 2 weeks this will be removed and we can start using new features.
We have changed a lot on system level though:
Windows 2003 x64 Enterprise Edition
SQL Server 2005 x64 Enterprise Edition
Storport Driver and MPIO
Next on the list for November is a whole new framework in .NET 2.0. Exciting times!