Olbermann's problem on MSNBC was always that being sandwiched between Tweety and Joe Scar meant that the only way he was going to get a decent audience was to become appointment programming - where people deliberately switch their teevee channel over to MSNBC at 8pm. Larry King and O'Reilly have long managed to accomplish that, but otherwise it's pretty tough thing to achieve on a cable news channel. But, recent ratings - with Keith consistently having a ratings spike - suggest that he's managed to do that.
Of course, stupid people like me have long suggested that the way to counterprogram a right wing news network was not to put on slightly less right wing programming, and that a left-of-center block of programming on MSNBC in prime time would spike their ratings, but no one listens to stupid people like me.
And, no, CNN with The Situation Room, Paula Zahn, Larry King, and Anderson Cooper does not qualify as a block of liberal programming.