Not reliable / usable for me. It complains about non existing errors - didn't find any images - which are infact there and are loadable for the UI. So how shall I test my theme for errors with the theme editor if the program didn't find the images which you should load fist?
Ok, I've looked into that issue. It seems to fail *only* if you load the wps directly, it works fine if you load the theme configuration (File / Open Project). However, if you load the wps other things will also be missing (most notably the font) since the wps file doesn't know about this.
Can you confirm this behaviour? From what I can see the problem arises when the Theme Editor tries to construct the base path when loading a wps file directly. This should be rather easy to fix. Without loading the theme cfg it will always look broken though. It might be a good idea to automatically search for a cfg file and load that if found.Edit:
I've changed the mentioned issue and uploaded binaries for Windows and OS X built from svn. Can you retry with that version again? Get it at http://www.alice-dsl.net/dominik.riebeling/rockbox/themeeditor/