The entries newsfeed contains the 20 most recent entries on the site, including blog entries, music reviews, and movie reviews, and all entries are provided in their entirety. Which means that, if you think Opus is an eyesore, you need never look at the site again.
The comments newsfeed contains the 20 most recent comments on the site, so you can keep abreast of any conversations happening on the site. (You can also subscribe to entries and receive e-mail notifications for subsequent comments.)
More info on Opus newsfeeds can be found here.