One of my clients wanted to use a SharePoint survey for a data entry form because the branching logic makes the end-user experience much better. Two problems:
1. The form requires a project code, for which this client has a site column, but you can't add a site column to a survey. We could do a lookup to a separately-maintained list of project codes - but that is terrible from a maintenance perspective.
2. There is simple workflow associated with the form, but surveys don't support workflows, even though the functionality appears to be there. I tested this with the built-in approval workflow and sure enough, "Failed on start."
Back to the drawing board.