Check this out:
http://www.newzie.com/Main screen:

You can turn the program into a news ticker:

You can search your big archive:

You can let Newzie delete all posts that are older than x amount of days:

It uses color codes to indicate how fresh a feed or post is:

You can set feed priorities and filter your feed view based on that:

And you can view some nice statistics about your feeds:

Although I like the program, I'm sticking with Thunderbird because I want to keep it simple and because it allows me to view my RSS feeds from within the same program I use to check my mail. Besides, it's a Windows-only app.