There's a lot of if's here so you can dig as you like. I moved 3tb in 200 databases in this case (Sharepoint databases). We used Hallengren's solution so I assume that if you don't have the large amounts that I have then you can always uninstall SQL 2005 cluster and install SQL 2008 and attach all the databases and import the users. But in this case it took it's time.

I did the checkdb and updatestats and prioritised checkdb first. The updatestats and reindex (included both in the Hallengren version we had deployed) the following night.

We tested different things as well. Remove the old clustername and just add a new computername to the clustergroup. Add a new CName record (or Alias record its called now) in DNS. For those of you who like clusters (I do) it is fun to test out these things.