I was amazed to read this about Movable Type:
The first problem I ran into was that the process of exporting my existing database and importing it into the new Movable Type installation did not preserve the IDs of entries. Unfortunately, entry IDs are used to construct the URLs of individual posts, which means that all URLs anywhere on the web pointing at specific entries would point to the wrong entry. For about 5 minutes I waffled on whether or not this was acceptable, but then I found these instructions on how to work around the problem.
Modifying the Movable Type source, exporting, putting out-of-order entries back into order, and inserting dummy entries to preserve IDs took about 45 minutes of tedious emacs work. Export/import that preserves IDs/URLs seems like a pretty basic capability.
I'm feeling a lot better about my object serialization scheme for saving entries now :)