I currently run PMS on WHS. I have a dual xeon 2.8 w/ 3gb ram on gigabit. I have streamed a 13gb bluray rip file shutter free with 5.1 audio. I installed PMS with default settings and I can stream almost everything in my library. I have a slew of different media types in the library and it plays about 90% of my library right now.
Kudos to the maker of the software. I know they have to be busy making changes, but I will put my name in the hat for a WHS add-in as well.
CUSTOM WHS SERVER
Supermicro server,Quad core Xeon, 4gb ram
Network: D-Link DGL-4300 Router, (2) D-Link DGS-2208 Switch
Stream HD content using PS3 Media Server to two PS3's