Well that's your answer.
If the "From" address is either the same as the "To" address, or is configured in GMail Settings as one of the 'Send As...' accounts, Gmail replies to the "To" address instead of the "Reply-To" address. An easy workaround is to specify a non-Gmail "From" address
http://stackoverflow.com/questions/2421234/gmail-appearing-to-ignore-reply-to
