OCC has published a review on the ASUS P7P55D Premium and P7P55D-E Pro

When it comes down to price, I would have to give the edge to the P7P55D-E Pro. Its feature set and performance are a match for the P7P55D Premium, but it just can't reach the same clock speeds with the stability I require, most likely due to the difference in the power circuits. Both boards are are full featured boards - each with a little something special. You can't go wrong with either of the boards if you choose to join the masses that have migrated to the Intel Core i5/i7 socket 1156 platform.

ASUS P7P55D Premium and P7P55D-E Pro Reviewed