It is hard to come to any real conclusion about the GIGABYTE P55-UD6, as we were not allowed to fire the board up and take it for a spin.
Looking at the physical layout, there are some concerns about space and useless PCI-E slots, but overall it seems to have a clean layout. The new socket on the P55-UD6 is a little awkward to use; when I was first playing around with it I was worried that I might actually scratch the board with the locking arm. This is not something to be taken lightly; as you can see in the enlarged pictures of the operation there are vital traces right below this arm. If one is cut you have a nice doorstop, but not much else.
On the features side, the removal of the SATA-6G controller is going to be a hit. True, there are no SATA-6G compatible drives out just yet, but it could make some people hold off on picking up a P55 and LGA1156 processor until they are ready and the controllers are working properly. I think this issue is really going to hurt adoption of this platform more than many realize. Yes, people will still buy P55/Core i5, but just not as many as might have if it were SATA-6G ready.
When the Core i5 is ready we hope to get back to the P55-UD6 in its more final form and give you a good indication of how it will perform for you. Until then we can say that while the P55-UD6 looks like it will be a stable and overclockable board, there are some design issues that GIGABYTE still needs to sort out to make it better.