Tab, sidebar implementation in NetNewsWire
 

If you can get a beta version of NetNewsWire 3, there's an interesting implementation of tabs and sidebar that may satisfy many a OW user.

After closing the last open tab, the sidebar will automatically disappear if "automatically show/hide tabs" is selected from the Tab menu. There's also a preference to jump from the last tab back to news items, instead of the previous tab. This might be a nice feature in OW, too. One could use the up/down buttons for proximate tabs, or delete a tab to return to the originary tab.

More germane to request made in this forum, there's an option to have tabs in the sidebar or on top.