best practice for providing newsfeeds ?

[Robert Koberg <rob@koberg.com>]

Hi,

What is the general best practice when providing newsfeeds with regard 
to type (RSS, Atom, ?) and version (RSS - v.91, 1.0, 2.0)?

If you could only provide one, which would you choose with regard to 
mass appeal?

Is this simply too political/philosophical a question to get good answers?

Is it a good idea to provide all versions or is it overkill?

What are some good sites to learn about best practices in this area? 
What are some good books?

We are going to add a newsfeed capability to our app. I am thinking of 
two ways to give the functionality to our users:
1. just generate all popular versions
2. give them a property/attribute to select a type+version (defaulting 
to the one with the most mass appeal)

thanks for any advice,
-Rob