OK, this is probably something very basic that I'm just not getting from the -h prompt of psarestore, but how do I backup a specific file or set of files from my psadump backup?

It's got to be a feature, but I can't seem to find it. All I can find is how to backup a specific client, but I don't want to do that, as there have been numerous file and database changes made since the last backup that I *dont'* want restored.

I believe you actually cannot. I know some people have messed around with it but I do not think there was any way/easy wayt o restore the files.

Only way you really can is to uncompress the backup file locally, and grab what you need from it that way.
The backup files would need a combination of Unzip and Unrar to properly open them, as they are stored in some stupid MIME, instead of a stabdard tar.gz like cPanel uses.
sw-soft really made this easy, huh?

yup nightstorm has got the only way to do it right there.