I am really into Google Reader and use it for a couple hours a day to help me read many hundreds of posts. For this it is a really great tool as it brings all of ones blogs and other RSS or ATOM feeds together into one place and allows really quick navigation vial keyboard shortcuts. It does not stop there as it also lets its users star, share and tag posts. The shared posts from a given Google Reader account appear like a simple blog or can be syndicated as a feed.
This is all great and wonderful but a problem, in my opinion, occurs when users want to incorporate some of their own information, for instance as an introduction to a given article on a shared feed or as comments to any article in their reading list. To do either of these things a user has to travel to an external website and use a inconsistent pipeline. Google Reader has further issues in that even bars the user form seeing comments on articles they read without traveling to the source of the content.
I think allowing of additions to posts in the form of both comments and sidecars to shared posts would be really convenient and would allow the Web 2.0 concept of social web to be more strongly upheld. I think the same is true of reintegrating existing comments into the feed view in Google Reader, without doing this I think we are taking steps away from social web ideals which seem to reduce the engaged nature of the social web.
Here is my main shared feed.