A key point of last week's season premiere was that Penny had never told Leonard she loves him. This week's episode kept the pressure on Penny, opening with the girls cataloging Bernadette and Howard's wedding presents. Their conversation turned to how Amy saw herself marrying Sheldon in exactly four years. Penny had no plans to marry Leonard, prompting the girls to ask if she loved him. She answered without enthusiasm, unsure what she felt was love. "Maybe," she said, "this is a new, better, boring kind of love."
I'm still invested in Big Bang after five seasons because Penny and Leonard's relationship isn't playing out the easy way. As close as they've gotten physically, Penny still has a problem telling Leonard how she feels.
Hearing that Penny was considering breaking up with Leonard, Sheldon tried to intervene. In previous seasons, he wouldn't have cared or might have even tried to bring on their breakup. Here, he showed concern for both Leonard's and Penny's feelings.
In the end, Penny failed to discuss her feelings with Leonard yet again, but I like that the show's focus has moved back to Penny and Leonard without feeling forced. Penny's complex feelings for Leonard show that theirs is Big Bang's most complex relationship while the others are more often played for comic relief. This also makes Penny and Leonard's relationship the most satisfying on the show.