Engler was one of my favorite professors at Stanford. He's kind, sharp, well-prepared, and consistently delivered great lectures.
One of the things that made him stand out to me are the insights he provided beyond what's in the papers we read in CS240. You can read the papers yourself, but the papers won't tell you things like "I think the reason this paper was accepted is different from the reason the author likely thinks it was accepted."
He's awesome, take his class. Find a good team, and, um, don't underestimate how much time CS140 takes. :)