The Bottom Half
There's plenty going on in this shot. First of all, see the seven SATA ports? Remember that the P55 PCH supports six? The two white ports connect to a--surprise--Marvell 6 Gb/s SATA controller. We just got word that stepping B2 of the P55 silicon was just received by board vendors, so it'll be interesting to see whether or not this feature survives Gigabyte's final revision. As we'll see in a second, Asus' offerings have already shed the controller. On a somewhat-related note, the latest stepping of the Lynnfield design has also gone out to board vendors, and we've seen 2.93 GHz parts clocking past 4 GHz.
Behind the SATA ports are three push-button switches: a large power button, a clear CMOS switch, and a reset switch. Though good for bench testers, they're all blocked by mid-range dual-slot graphics cards like the GeForce GTX 260, unfortunately.
Also note the unassuming little heatsink covering Intel's P55 PCH. For all of the fancy coolers we've seen up until now, this is really all the core logic component really needs.