I would think that this isn't so much of a case of the newsreader itself as it is on how much bandwidth comcast is allocating per person.
For a long time I liked the newsreader that was bundled into Netscape. But with version 7.0 that reader became a major dog. Slower than whaleshit. I'm not sure why such a great little program got ruined like it did, but it happened. I've not yet found a suitable replacement for the program either.
If you're browsing the newsgroups for pics check out www.newsdump.com. Its cheap and organized for easy downloads. Don't know about uploading. They also have mpeg's.
Not sure which you mean, but I got Xnews to decode yEnc files in News Groups. It is free and works well after a little setting up. http://xnews.newsguy.com/