Dino has put together a great article : "Rearchitect Your Web Applications for Microsoft ASP.NET 2.0" in MSDN.
Bottom line:
ASP.NET 2.0 comes with a full bag of new goodies and features to write better applications, possibly faster. So migrating to 2.0 is definitely going to be a great experience for most developers; the point is, how seamless will this migration be?
Definately worth a read.