While the CSOM code above likely can be made to work I find it easier to use the web client method.
(from http://soerennielsen.wordpress.com/2013/08/25/use-csom-from-powershell/)
I've used the code below, to retrieve a bunch of files (metadata from CSOM queries) to a folder (using your $result collection, other params should be adjusted a bit):
#$siteUrlString site collection url
#$outPath path to export directory
$siteUri = [Uri]$siteUrlString
$client = new-object System.Net.WebClient
$client.UseDefaultCredentials=$true
if ( -not (Test-Path $outPath) ) {
New-Item $outPath -Type Directory | Out-Null
}
$result |% {
$url = new-object Uri($siteUri, $_["FileRef"])
$fileName = $_["FileLeafRef"]
$outFile = Join-Path $outPath $fileName
Write-Host "Downloading $url to $outFile"
try{
$client.DownloadFile( $url, $outFile )
}
catch{
#one simple retry...
try{
$client.DownloadFile( $url, $outFile )
}
catch{
write-error "Failed to download $url, $_"
}
}
}
The trick here is the $client.UseDefaultCredentials=$true
which will authenticate the webclient for you (as the current user).