I've had two content streamers over time (DLink and Popcorn Hour). I'm converting to HTPC in the next month.
You cannot guarantee the consistency of support for a content streamer. With an HTPC, you are your own support. You aren't dependent on someone else for firmware updates, bug-fixes, etc. from a company that may or may not get it right (and I've seen what happens when they don't).
I'd much rather run a PC with XBMC or Windows Media Center after several years; there's more flexibility and I can choose what I want for power configuration. Also, if you're serving up your video from a Windows box, setting up file shares is nice and convenient.
I'll be posting my project once all of the parts come in.
Core i7-2600K @4.2GHz, GIGABYTE GA-Z68XP-UD5, 4x4GB G.Skill RipJaws PC1866
Corsair 650D case, Seasonic X750 Gold PSU
WD `Raptor 600GB boot, WD Caviar Black 1TB data, NEC 7200 DVDRW
2x Radeon 6970 2GB in Crossfire, X-Fi Titanium, Dell 2407WFP