Haven't tried antiword. As of now I find abiword pretty stable for both doc and docx. I need more data but I found a few cases where it just hanged while converting. There is no specific pattern to when the program hangs. For now I am logging such cases and timing out the conversion in 3 seconds.

Thanks.

Where do you get your doc files?

Are they the just ones submitted to your site, or is there a pastebin or similar repo of doc files?