I like the tabbed MDI interface of Xnews. I've got it set up for 5 servers, and each is just a tab to click on. Within each server I have as many as 40 subscribed groups, sorted into folders I keep closed unless I want to view them.
Some of the features are a little harder to find, and it's a bit clunky-looking compared to some of the others, but I guess its like a command-line interface, once you learn the tricks it can be very fast (but you have to want to learn the tricks).
It takes me about 15 minutes a day to view the titles of every post in every group I normally monitor. Obviously longer if I get into a thread or want to reply.
It also dings at you if anyone replies to one of your posts
I used to use Xnews, Agent, and Gravity all simultaneously for different purposes. On an old website I used to run I'd post selected articles into a database for my web users to browse. Agent was excellent for that. Gravity was used for searching for specific topics (but dejanews (aka google) made that pretty much obsolete).
Oh yeah, I also use NewsbinPro, but that's not technically a reader. Its a robot that will go into groups you select and download binaries using criteria you specify.