Here is the plist I am using.
<?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>Label</key>
<string>io.upspin.upspinfs</string>
<key>ProgramArguments</key>
<array>
<string>/usr/local/bin/upspinfs</string>
<string>/Users/mennis/u</string>
</array>
<key>StandardErrorPath</key>
<string>/Users/mennis/stderr.log</string>
<key>StandardOutPath</key>
<string>/Users/mennis/stdout.log</string>
<key>UserName</key>
<string>mennis</string>
<key>RunAtLoad</key>
<true/>
</dict>
</plist>