P&K gives you something that year 1 of law school sorely lacks: a context for the fragments in your case book. Its treatment of Palsgraf is particularly beautiful.
And since Prosser so strongly influenced tort law, you can be confident that you are getting good information. Some of my classmates used commercial outlines and they often worried about whether they could trust the material. No such problems with P&K; it was on the money all the time. And when there was a contradiction between P&K and my textbook, I was able to go to my professor and ask her about it. Try doing that with a commercial outline.
P&K is not merely fine reference tool; it is a genuine work of literature. I love it, and I highly recommend it.