cat <<-EOF >~/Library/LaunchAgents/net.iharder.shareitunes.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>KeepAlive</key>
  <true/>
  <key>Label</key>
  <string>net.iharder.shareitunes</string>
  <key>ProgramArguments</key>
  <array>
    <string>dns-sd</string>
    <string>-P</string>
    <string>Local iTunes</string>
    <string>_daap._tcp</string>
    <string>local</string>
    <string>3689</string>
    <string>localhost.local.</string>
    <string>127.0.0.1</string>
    <string>Arbitrary Text Record</string>
  </array>
</dict>
</plist>
EOF

sudo cat <<-EOF >/Library/LaunchAgents/net.iharder.shareitunes.plist
...

Paste to terminal is one step.

Finding the folder, creating the file, pasting, and saving it is 3-4 steps depending on how you count them. Then you have to paste the launched line in the terminal anyway. Knowing how to even go to the Library folder, and how to make plain text files are hurdles that a lot of Mac users might not be well versed in.

I do like your EOF file format though. If I were re-submitting the hint, that's the method I'd propose.