My database is now at compatibility level 90; I asked the ISP tech support if they could upgrade it and they did so. Apparently all I have to do is ask. They won't be ready to roll out SQL Server 2008 for awhile so 90 is as far as we go now.

I'm thinking seriously of upgrading my test site to SQL Server 2008, now that my database is at compatibility level 90. Since I would never under any circumstances try to rebuild the production site from a backup of the test database (I'd do it from the ISP's nightly backups), I don't think the inability to restore to 2005 from 2008 would be an issue.