Attensa is aggresively adding features to compete with other readers and has an excellent product suite. However, some (including Jeff Nolan) have stopped using Attensa’s Outlook product because of reported difficulties in making these third party applications work with Outlook properly.
I tried to use Attensa myself today and was very impressed with a number of the features, especially the tagging functionality. Unfortunately, I couldn’t get it to update any of my feeds, no matter what I did. I’ll still check back with the product down the road when they work out the kinks, but right now it just doesn’t seem mature enough to use.