When I use Form(enctype="multipart/form-data"), the newlines of a
textarea are duplicated each time the form is submitted. Since I have a
preview button which shows the same form again, each time the button is
clicked, the textarea appears with double the spaces between the lines.

With just Form(), there is no such problem. I'm guessing the problem has
to do with http_request.py, line 232:

             _add_field_value(self.form, name, '\n'.join(lines))

Which seems to add extra '\n's. But I'm really not sure of the entire
multipart processing logic - still looking.

Another nitpick - the __version__ in __init__.py for 2.0a3 is still '2.0a2'.

Cheers,
Shalabh