OK, because the Cayman is basically the Boxster with a roof and 10 more horsepower, let's compare Boxsters first. The 987 was designed around plain old 911 doors, like the original 986 from the '90s was. That means the sides are plain in general, because of Porsche's smooth, clean aesthetic (for its sports cars, at least). The key difference in the 981 is that the Boxster was granted its own doors, so with that freedom they deeply embedded the main air intakes, giving it the gradual dip into the car. They also made the characteristic rear arches a little more curved and pronounced in profile, while adding the double-decker headlights, à la 918 Spyder and updating the three front bumper grilles to fit with the new shape(s) better, giving clearly defined "cheek bones" in the process. Of course, my favourite touch is the rear LED lights, which have the pop-up spoiler arching down into them at the ends to make the reversers, which looks very smooth and very cool. The roll hoops are also chunkier and more shaped, possibly for aero reasons but I don't know if that's really why that is.
To make the Cayman, they added a fixed roof - which is now more 911-shaped in that it arches down more smoothly to meet the waistline at the spoiler, rather than having that dip in the middle of it where the rear window ended - and a reprofiled front bumper with less smiley/more aggressive Down-the-Road Graphics (DRG), or "face". As with the 987, the rectangular foglights have been replaced with a dot in the bumper grilles for the hardtop model.
So there. Just because it's evolutionary rather than revolutionary, doesn't mean they aren't trying. You just have to be paying attention for about two or three seconds. Here are some more pictures, because it looks great. The mostly-subtle changes really make a difference in my opinion.