The biggest down fall to the P8H67-I is the fact that it indeed lacks the ability to adjust the multiplier on the K series CPU. Saying that, we knew this before we got the board and it's not a limitation of the board itself, but the chipset by Intel.
From our testing we know that at stock most of our P67 / Z68 boards perform almost identical to each other. Paying more for one board over another usually does two things, bring with it more features and the more expensive boards carry better cooling around the CPU area which normally allow for a higher overclock. We saw that with the Maximus IV Extreme-Z which allowed us to achieve 5.38GHz.
At stock, you can see that the P8H67-I manages to perform well; it actually performs in line with more expensive boards. Of course, it's limited by overclocking, and being a mITX board, features are a little lacking. In this case, though, it's really only connectivity and to be completely honest, the size of the board is a feature in itself and if you're looking for a mITX solution, then it fits the bill perfectly.
What surprises me is the fact that in our video card testing the board performs just as well when running at stock. We've already mentioned this, but due to the fact the board carries a x16 slot that is wired at x16, the performance is extremely strong and you can see even with a high end card like the GTX 580, the performance lines up with other boards using the 2600k CPU and a GTX 580.
Paired up with something like the i3 based line from Intel, the P8H67-I has the ability to really be as powerful as you want it to be. The fact that it has no problem holding our Corsair H100 cooler and the GTX 580 is great - the fact that the whole thing performs like it does, though, is fantastic.
If you're looking for a mITX board that can pack a series punch and you have no need for overclocking, the P8H67-I is a fantastic option from ASUS. I think as the months go on, we'll see more and more companies offer us performance based mITX boards. While the expansion possibilities are indeed limited, they can handle a top end video card and teamed up with a good processor, you can see the performance we're able to get out of the system.