Hi there,
I counted the "<revision" tags in the current 20110901 pages-meta-history (bzip2) and got the result 412,482,641. Using http://www.wikistatistics.net/wiki/en/edits/90 for verification (which works fine for smaller dumps), there should be around 482,500,000 edits, however.
Are some revisions, e.g. minor edits not included in the dump?
Kind regards, K. Mueller