Things to check:

Release message template: 

To:     mercurial <mercurial@selenic.com>
Bcc:    lwn@lwn.net
Subject:        Mercurial 1.x released!

Full details here:

http://mercurial.selenic.com/wiki/WhatsNew

Available for download at:

http://mercurial.selenic.com/release/mercurial-1.x.tar.gz

Binaries releases to follow shortly.

Generating a list of new contributors: 

comm -2 -3 <(hg log -r '1.5::' --template '{author|person}\n' | sort -u) <(hg log -r '::1.5.4' --template '{author|person}\n' | sort -u)