I am NOT a systems administrator for the SharePoint
Site in question. Therefore, my knowledge of the actual migration steps
below is second-hand.

We are planning a migration of 2003 SPS and WSS sites to 2007 MOSS
Enterprise. As part of the preparation, our systems administrator preformed
a "rehearsal" for the actual migration: he created a "clone" of the site on
separate hardware, then applied OS upgrades and MOSS upgrades, then migrated
the sites. I am part of the team testing the new sites for compatibility
with the old sites.

The first thing I noticed is that sites which had other-than-default themes
in the 2003 instance no longer had them in the 2007 instance (unless the
pages were unghosted in 2003). Is this to be expected, or is there some
step we missed in the migration process?