Most feed readers only know how to handle RSS and Atom.
Some of them might support XML extensions commonly used by feeds such as Dublin Core or wfw:commentRss but as new extensions become popular, you have to wait for the developers to add support for them, if it happens at all.
And you know there's no way they'll be adding support for your in-house, proprietary extensions.
Awasu's metadata modules let you extract and process any information embedded in your feeds.
This additional metadata can then be used throughout the system e.g. you can show it to the user or have your channel hooks process it.