The two issues I'm seeing are...
1 - It doesn't work with all types of feeds. Here's one example:
http://forums.anandtech.com/rss.aspx?forumid=1&catid=40
2 - The order of items should be descending (newest to oldest) and often times isn't. I've seen this with Digg, my own site RSS feed, and a few others.
Any help would be greatly appreciated.