Alternatively, you can creat a folder on your bookmarks bar with each of your rss feeds. Then you can still see the number of new articles. Then Command-clicking the folder on your bookmark bar goes automatically to the "View All RSS Articles" link. Since i have my middle mouse button mapped to Command+Click, middle clicking also works for me. I'm not sure that is default behavior though.

This is what I did also, using my programmed command-click trackball button.
One advantage to creating your own folder in the bookmarks bar, is you then can place the RSS feeds in an order other than alphabetical, as the "All RSS Feeds" collection does. This order will appear in both the bookmark bar folder menu, and on the RSS sidebar.

I'm now experimenting with using the auto-click checkbox instead of command-click to show all feeds, as this is the action that I usually do.