Drawback of Kullenschliff (Granton) knives
The biggest downside I can think of was touched on in the top answer to the question Catija:


  In fact, the thickness of the blade tends to have more of an effect than the voids in most cases.


Specifically, in order to have room to add those air pockets without them just being holes, the blade has to be thicker. This is a potential downside in a couple ways:


If you're cutting something big and sturdy, the knife can get wedged in more easily. Winter squash might be the best example. When you're halfway through, the squash is squeezing together on the knife, so it'll be harder to force a thick blade the rest of the way through than a thin one.
If you're cutting something delicate, you'll mess it up more. For example, crumbly or flaky desserts tend to fall apart more when a thick knife blade is forced through them than a thin one.


Of course, thicker blades are also usually heavier (probably still are even with the removed bits), which also has pros and cons. Nothing's ever simple!