Like Google Reader, Bloglines is an excellent RSS tool. Its frame-based interface may look slightly more old-fashioned, but this doesn't slow things down. It's extremely fast, very fluid and offers everything you need for tracking your feeds.
Unfortunately, Bloglines is a perfect example of how a product can do almost everything right but still struggle to take the top slot. In this case, Google has been far faster to update its system with new features and UI choices, leaving Bloglines to trail behind somewhat.
Does this matter? Not really. Everything works well, its support for clippings is almost exactly the same as Google's and the only important feature it's missing (depending on how you use RSS feeds) is the ability to comment on stories and share them with friends.
Bloglines also uniquely offers email subscriptions, which enables you to sign up to online newsletters and mailing lists and have them delivered straight to your RSS reader instead of your inbox. It's a genuinely useful feature, even if mailing lists have mostly been superseded by the world of blogging and RSS.