Benchmark Reviews posted a review on the Gigabyte GA-P55-UD6 Motherboard

For computer enthusiasts, the last Intel milestone was the Core i7 processor launch that paralleled the X58-Express motherboard chipset launch back in November of 2008. Ten months later and well into September of 2009, Intel has returned with the P55-Express chipset for mainstream users who pair it with the new LGA1356 socket. On the outside little more than the processor socket and memory configuration has changed, replacing dual-channel for triple. PCI-Express now offers only one 16x lane instead of two, while the number of SATA and USB ports continues to give more expansion room than the average user might need. The consumer might not know what to expect when choosing between the two products, other than one is mainstream (P55) and the other is for extreme enthusiasts (X58). In this article, Benchmark Reviews directly compares the Intel Core i7-860 equipped Gigabyte GA-P55-UD6 motherboard against the GA-EX58-UD4P with Intel Core i7-920. Testing a Core i7-860 against an i7-920 might not seem fair, and it's a little biased to compare P55 against X58, but the final outcome might just surprise you.

Gigabyte GA-P55-UD6 Motherboard: P55 vs X58 Review