I wanted to say how much I like doing the vocabulary Flashcards.
I tend to use the review page from every lesson to make a deck for that lesson. I find this helps me work out which lessons I've not been attentive enough to and need to repeat.
I tend to use Anki for learning my Kanji and one thing that stands out with their flashcard system that could be used on JapanesePod101 is the addition of various views to help track your vocabulary. So you can see how many words you've mastered, your increase plotted over time etc.
I personally find that if I look back over charts like this and can see that a month ago I had mastered say 30 fewer words it helps give the inspiration to crack on.
At the moment I can only see what I've studied/mastered etc when I begin a study session on a deck.
Thanks for all your hard work!