So I've built my first HTPC ever with this board. I chose this one for two main reasons:
1) I've build with Asus for many years
2) Fanless design should be quiet for HTPC use
I got the P7H55-M PRO from Newegg the day it was released.
I'm overall impressed with this board. Small but it doesn't feel "cramped". SATA connectors are in good spots and there are 6 of them. There are 2 fan connectors besides the CPU fan so if you have more fans you'll need to connect them to your power supply.
Only two issues that I see for some people:
1) Will only support a graphics card of 10.5 inches or so or it can interfere with the SATA ports.
2) The CPU heatsink/fan is very close to the memory slots. If you fill all 4 if you have "wide" SIMMS you may run into an issue. But if you stick with just 2, don't have massive heatsinks on your memory or choose your cpu cooler carefully you shouldn't have an issue.
I would recommend this board to anyone building a HTPC just in terms of putting it together. I will be firing it up today and installing software so I'll add more once I do that.
Below are some pictures. All my hardware for this build:
Case: SILVERSTONE GRANDIA GD04B
PSU: Antec BP550 Plus 550W
MB: ASUS P7H55-M PRO LGA 1156 Intel H55
CPU: Intel Core i3-540 Clarkdale 3.06GHz
Memory: G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
Hard Drive: Western Digital Caviar Green 1.5 TB
Graphics: On board MB
Sound: On board MB
Blu-Ray: LG Black 8X BD-ROM
This is a very nice case by the way. I took my time to route cables and it gives several options to do so. I spent a bit more for a modular PSU but well worth it in a cramped mATX case.