There's a really informative article over at iFixit titled, "Apple Engineers Its Own Downfall With the Macbook Pro Keyboard". This is a really good summary of a current issue with Macbook keyboards that's generating a lot of complaints.
I'm seeing a lot of this myself. Even on a good day, there seems to be a general detest towards the redesigned Macbook keyboard due to how it feels. Basically, there's virtually no "travel" (the amount of movement the key does when pressed) which makes it feel like typing on a solid, hard surface with no tactile feedback. But on top of that, these new keyboards are very prone to failure, with the slightest speck of dust seemingly all it takes to cause a key to stick, not feel right, or not work at all.
Making the problem even worse is the fact that the keyboard is not a replaceable part itself. Instead, Apple has decided to make the keyboard part of the overall chassis that also contains the glued-in battery. As a result, any repair to the keyboard or battery requires an increadibly tedious repair and an extremely expensive part.
While Apple now has admitted fault and is offering an extended repair program, there is nothing we're seeing that suggests that the replacement is any different than the original. So the underlying design problem will remain even after repair, suggesting that the problem will continue to plague users until they can no longer get their free repairs and just give in and buy a new computer.
As always, I encourage my clients to carefully consider repairability, total overall cost over the life of the laptop, and design/business philosophy of the company when making computer purchase decisions. All this should play an important role in the decision making process as it will affect how pleasant your experience will be with the computer and how much money you'll be spending in total over time to maintain it.