The new K series CPUs are not bringing much to the table that will give you better stock performance. These CPUs are not meant for the average consumer. They are meant for the person that wants to push their CPU as far as they can. The same group of people that are going to run liquid or phase change cooling will benefit from this line-up. Even the casual overclocker is only going to get a small boost from this (as our air cooled testing shows).
Still, we do know that the i7 875K is capable of getting much farther than the average 1156 Core i7. Our previous experience with the i7 870 only allowed us to reach 4.2GHz before the system would not even post. Now, on the same air cooling we are hitting 4.5GHz for CPU-Z shots and stable performance at 4.1GHz. This is a good indication that you will get what you put into these CPUs (in terms of cooling).
We do hope to return to the 875K and test it out again under some good water cooling just to see how far it will take us. The pricing is also not extreme, with the 875K coming in at around $324.
These CPUs from Intel should give the overclocking community a new toy to play with for a few months and keep them very happy.