Yes, I see THAT feed validates, but what about my feed? Try it and you'll see what's wrong: http://www.davidmattison.ca/wordpress/wp-atom.php
As I said, before I tweaked it by adding the encoding="UTF-8" to XML declaration, the feed wouldn't validate.
It's presumably the same d*d file (except for the addition of the encoding="UTF-8" attribute that appears to be necessary according to the Atom 0.3 spec).
The other issue here is that the Atom feed from http://fresh.wordpress.org (nor my site) is not being recognized by NewzCrawler's Atom/RSS Autodiscovery mechanism. No doubt because http://fresh.wordpress.org/wp-atom.php does not appear in the Meta section or anywhere else except in the Head/Head section, which doesn't do any good. Interestingly enough, although my RSS feeds are recognized by NewzCrawler's autodiscovery, the ones from Matt's site are not being recognized.
I can add my Atom feed manually and have it parsed by NewzCrawler, but when I try to validate the feed through NewzCrawler's built-in link to the Feed Validator, I get the same error, plus, I just discovered, this new one:
line 5, column 30: modified must be an ISO-8601 date [help]
There's a caret pointing to the "Z" that I haven't included.
BTW, matt's sandbox also appears to be broken today (Jan 6, 2004), as there's a whole bunch of MySQL query statements after the credit line! ;-)
I see there's now a note about some users having issues with release 1.0 and that a bugfix will be released. I'll grab the latest wp-atom.php from the CVS repository and see if that makes a difference.