This could be a bug with InfoPath but I think it's more likely that there is some some confusion between "design a form" and "filling out a form"?
dlgross: when you say they print with print preview and when you print as well, is that when you are designing the form or actually using the form (filling it out as a user would)
Submit buttons, date picker controls don't show up when I actually fill out a form and print it out, but they DO show up and printout when I print preview and print from when actually designing a form.
If they are only showing up for you in design view then I would suggest that this is a designed feature of InfoPath to allow designers to print out forms and know what kind of control is there on the form.