The following MSDN article is a primer when considering upgrading from one DB Engine to another in SQL Server

http://msdn.microsoft.com/en-us/library/ms143393(SQL.90).aspx

Thanks

We still have problems to find a stable version, we have migrated from 2000 to 2005 a year ago, but have several problems with a lot of maintenance plans bugs after upgrading to SP2. After that we have tried Cumulative Update 4, but I have already heard from CU 9! Our problem is to upgrade to a stable version after SP2, since SP2 is not acceptable with severe maintenance plans bugs in it, like integrity checks (only master!), wrong cleanup etc.
But it looks like that CU4 is acceptable for us, but for one particular application it will be CU9, and this application still works fine on SP1.
After a year of migrating to SQL 2005 we have advise of Microsoft consultants to migrate it to SQL 2008 because it will be better and more stable. I think this is to fast for our company with such a short lifecycle!