Just finished by first HTPC build:
Silverstone GD05B case
Asus P8Z68-M Pro mobo
Intel Core i3 2100
Scythe Big Shuriken CPU cooler
G Skill Rip Jaws 4 (2 X 2)GB Ram
Sea Sonic PSU
Crucial M4 SSD (for OS)
Recycled 100 Gb 2.5 drive from laptop (little storage)
LG BD/DVD combo drive
Ceton InfiniTV 4 Quad tuner
Logitech Harmony 7 with HP IR reciever
Win 7 64 bit and Arcsoft TMT5
Observations of the Ceton tuner: I first had a cable splitter setup (one to my HTPC and one to my modem/router) but immediately noticed pixilation and interference anytime there was internet traffic. So I removed the splitter and moved my modem/router to another location in the house, and that solved the issue.
So far, the card is working great in WMC. I have only had 2 instances of pixilation since then, which I had experienced before even with a Comcast box. I will continue to keep an eye on that as it could be caused by other things as well.
Comcast setup only required 2 calls to them - first lady flat out told me she hated setting up cable cards! She was a self fulfilling prophecy as I had to call back again!
The only other issue so far is when I boot up, it takes a few moments for the tuners to "load" so I think by keeping the HTPC on will take care of that.
All in all, pretty awesome!
I haven't recorded anything yet or setup any Xbox extenders, but for the simple fact that I don't have a Comcast box is well worth it!