I've been playing with the newest build (Alpha 3) and so far so good but (you had to know that was coming :) ) I have a few suggestions or feature requests.
1. Collapsible subscription headers - I normally use GReader with all the 'folders' collapsed and then scroll though the posts in each of the subscriptions. For someone with a lot of feeds coming in displaying all the individual feed titles in
the subscription pane on the left uses a lot of valuable screen space. - http://screencast.com/t/JvPzibrf
2. Double clicking on the grouped subscription header - it would be nice if when I double click on the group folder that the message list pane display all the unread posts from feeds in that group - http://screencast.com/t/HzwB8cwqmK3
3 - messagelist display - this could be an option setting but it would be nice if instead of just having the unread post title, image, and brief excerpt if we could select to display the whole post in that area rather than having to click through - http://screencast.com/t/TfO0CwtL5B
4 - auto mark read option - this again could be a user selected option but it would be nice that as you scroll through, or leave a feed display, if the displayed posts could automatically be marked as read.
Two things that I have noticed as missing are support for Shared items and tagged items but I am assuming that they are on the roadmap.
I'll be playing with this some more most definitely because I really like what you have done so far so I will probably be back with more suggestions :)
If you wish you can also contact me off list at email@example.com - keep up the great work