I've recently decide to switch back to pair Networks and ran into some issues getting Drush setup via the new Pear method. Here are my notes -

1. First, setup some sane Pear variables for the shared environment -
   pear config-set bin_dir ~/bin
pear config-set temp_dir /tmp/<username>/pear/temp
pear config-set cache_dir /tmp/<username>/pear/cache
pear config-set download_dir /tmp/<username>/pear/download
2. Now, follow Drush setup instructions for Pear and run the following commands -
   pear channel-discover pear.drush.org
pear remote-list -c drush
pear install drush/drush
3. Setup Drush to use higher memory_limit and other good settings -
   mkdir -p ~/.drush
cp ~/pear/drush/examples/example.drush.ini ~/.drush/drush.ini
4. Last bump PHP's CGI memory_limit up to 128M as well -
   cat > ~/public_html/fcgi-bin/php.ini <<EOF
memory_limit = 128M
EOF

Easy enough!