As reported:
http://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28technical%29#iPad_now_redirecting_to_mobile_site.3F
I can confirm on en.wikipedia.org and fr.wikipedia.org and my iPad running iOS 4.2.1.
(Note that 1.17 upgrade is in progress but should not affect this redir issue, afaik)
Version: .5
Severity: enhancement
URL: http://en.wikipedia.org/