What's the easiest way to install Mercurial 1.5.1 on Debian Lenny? Can I safely install the package from the sid repository using apt-get, or should I compile it from the sources?
Hmm; looks like backports.org doesn't go newer than 1.3.1 right now.
Given that, the safest approach is to build from sid's source package (so you'll still have a debian-packaged binary, just one you built yourself); see http://www.debian.org/doc/manuals/apt-howto/ch-sourcehandling.en.html for a quick primer
If you've added the sid source repository to your sources list, you might also consider using