Quick post to consolidate information around the net. Installing this package is not as straight forward as most, as it’s in the beta channel.

Failed to download pear/Spreadsheet_Excel_Writer within preferred
state "stable", latest release is version 0.9.1, stability "beta", use
"channel://pear.php.net/Spreadsheet_Excel_Writer-0.9.1" to install
Cannot initialize 'channel://pear.php.net/Spreadsheet_Excel_Writer',
invalid or missing package file
Package "channel://pear.php.net/Spreadsheet_Excel_Writer" is not valid
install failed

Behold:

pear config-set preferred_state beta
sudo pear install ---onlyreqdeps Spreadsheet_Excel_Writer

Include the onlyreqdeps switch so that the dependency package PEAR OLE is installed.