BloglinesFrom what I gathered, Bloglines seems to be the most popular service online and generally I think it's ok to use, no more, no less. I don't like the layout using frames, although I really have to give them credit for their excellent PDA version (the only serviced I've had the opportunity to test on a PDA). My preferred usage is to keep my read and unread posts together in the order they were posted by the author, together with an indication in the navigation of how many unread posts there are in that specific feed. Bloglines, as well as all the other services have that indication. However, one thing that bothers me is that the read feeds disappear from the default view when I click on a feed. It is possible to retrieve them again, but that requires extra steps. An alternative to this is to use Clippings to save your favorite posts, but that's not as interesting to me.
NewsGatorNewsGator is very similar to Bloglines but with a slightly more appealing layout. It implements the same things with removing read posts from the default view and having Clippings for favorites. The thing with NewsGator, though, is that the whole feed disappears from the left hand navigation, if it doesn't contain any unread posts. Very annoying.
Google ReaderGoogle Reader has a default layout which is very sparse but good, and it displays only the latest updated posts. It also has support for keyboard shortcuts, of which I'm a real aficionado. But, as soon as you click the Your Subscriptions link, it takes up the entire top part of the web page. I would really like to see a way to check posts feed by feed without losing so much space of the web page. Google Reader definitely has potential in my eyes, though.
RojoFirst, I love Rojo's front page with the Most Read Stories and Recently Tagged Stories, it's a great and simple way to see what's talked about right now. Rojo has also taken a little different approach with tagging posts, something I really like and it makes it very easy to find mine and other people's posts for a certain topic. After that you have a number of ways to view your feeds, and the different options you make should stick. Unfortunately, expanded blocks in the Feeds tag view doesn't seem to be consistent/stable when it comes to that, but otherwise it works fine. Overall, it does seem just a tad slow, though.