I get lots of questions all the time about upgrading from SQL 7 or 2000 to 2005. I can tell everyone that so far most of my customers have gone through the process without incident. The product group really focussed on the upgrade scenerios with SQL Server 2005, and honestly, it shows; the whole process can usually be described as 'mostly harmless'. ;-)
For those of you who want to read some best practices of others that have migrated, we just released the SQL Server 2005 Upgrade Technical Reference Guide. It's a great reference that covers:-
It's around 350 pages, and well worth a read if you're feeling a bit jittery about the upgrade and need a technical security blanket to pull you through. Download it here.