This isn't really an important issue, but I kind of miss the old opening theme. It was simple and quick. This current theme song is longer, and makes me want to roll my eyes, with its weird techno feel. I would be a little embarassed if I was listening to a lesson, and someone next to me overheard that theme song. I think in the case of an opening theme, less is more. And I don't think the new theme song really appeals to the main demographic that uses this site (though I don't have any special insight into that).
As for my new feature suggestion, first I think it would be a good idea to implement video or interactive lessons that use a similar learning technique as Live Mocha, or Rosetta Stone. While the visual-learning method they use isn't good enough to stand on its own, it is excellent at helping people learn vocabulary, and retain the information by providing a visual reference that helps them remember the new words more effectively. It does a poor job at teaching grammar, and when used on its own, causes a lot of confusion, when someone needs more details, but I think it would be a wonderful supplement to the current lessons.
My second new feature suggestion, would be linking the different language sites like japanesepod101, englishpod101, russianpod101, and others into a language-exchange community. People learning different languages want to speak to natives of the language they are learning. Creating a language-exchange section that is common to all the sites, would bring these people together, and I think increase the number of subscribers, who want to practice their new-found knowledge with others who speak it as part of their daily lives. There are already sites out there that do that, but I think it would be a great feature for this site and the other sites to have.
Finally, there is no single method that works best, for learning a language. But if multiple methods are combined into a single site, it can provide the one-stop location many people are looking for, when learning a language. I think it's important not to get so caught up in a single good idea, the way Rosetta Stone did, and ignore the other good learning methods, that work equally well. When put together, the different methods form an excellent whole-language learning solution.
Anyway, those are my suggestions