The RSS feed only includes 15 items (in order to meet with the standard as I understand it). Unfortunately when the number of revisions > 15 it only shows the oldest revisions.  Dopey.

Fixed in v0-0-4

Fix is in templates/default/views/Page_rss.rhtml

Replace
<code>
for revision in page.revisions
</code>

with 
<code>
page.revisions.reverse_each do |revision|
</code>