InfoPath Dev

I know that documentation is generally the last thing on a developers mind but has anyone developed a Detailed Design Document for documenting how your InfoPath forms are designed?

We haven't done my Design Documents for InfoPath forms, but we have done user manual documentation. The reason there is generally not much design document for a Form is because it is so data-based. The only thing that needs to get documented is the Schema and that is done with the Data Source task pane. On top of this, everything is just action event listeners which when commented correctly should usually explain themselves. For forms we normally have a Specification document and then just look at the code and schema for the form itself.