I have been using Google Reader for about a year now, and I love it. The convenient keyboard shortcuts (j, k, and s) make flying through a backlog of posts a breeze. Plus, I just like Google apps for anything that is not overly sensitive. I do not use Google apps for business, for example.
Still, the desktop readers from NewsGator sound like great options. And, of course, you can read feeds within Outlook and Thunderbird, already, if you just want to stay within software you are already using. Check out the review and decide if you should be using something different.