Back To The Future Episode 2 is an essential purchase for fans of the movies and, of course, the first episode. It has the same strengths and, particularly for first generation iPad owners, the same weaknesses too.
It is a safe bet that proponents of the first episode will likely enjoy Episode Two, and if Telltale's track record in the adventure game genre is any indication, the whole Back to the Future game series is likely going to reach classic status down the road.
Like I said, fans should dig this one; detractors won't. "Get Tannen" does nothing super special other than add to the fiction, which I imagine would be fine for everyone who enjoyed the first installment of the game series and are looking for more.