I'm seeing what seems to be a bug:

If I export a simple document to ODT with the following settings:

#+EXPORT_OPTIONS: H:3 num:t

The headings are given a proper heading style.

However if I export with:

#+EXPORT_OPTIONS: H:3 num:nil

The headings appear in "Default Style" (the body text is in "Text
Body"). In short: setting `org-export-with-section-numbers' to a non-nil
value is necessary to get the headings styled with a heading value --
otherwise they're default style.

The "contents.xml" file in the two different versions differs only like
this:

text:style-name="Heading_20_1_unnumbered"

vs

text:style-name="Heading_20_1"

That seems correct. I've attached a diff between the two different
versions of the "styles.xml" file.

I don't know much about ODT format, and don't know what's going on. I
traced `org-odt-headline', and it appeared to be behaving normally.

I'm using git Org, and the current Libreoffice version (on Arch linux)
is 4.4.5-2.

Any hints appreciated!

Eric