I have noticed some strange behavior with accessing rss feeds with NetNewsWire. When my wife mentioned that she posted a new article on her blog, the post didn't show up in NetNewsWire, even after refreshing.
I found out what the problem is. Synchronizing with NewsGator is causing the problem. Not only is the read/unread status, but when synchronizing is enabled, all rss feed requests are proxied through NewsGator, and it looks like the feeds are only refreshed once an hour.
It seems strange that they would do this, especially since they are incurring the bandwidth hit for every installed NetNewsWire that has NewsGator synchronizing enabled. The only think that I can see that they are tracking requests to the rss feeds for their statistics.