Step one in streaming is, of course, authorizing your PS3 to access your media on your Vista box. Gone are the days of the oh-so-simple folder sharing Windows Media Connect app, though; now Windows is much more active in managing your library before streaming it, meaning it's not as simple a process as granting your PS3 access and letting it go crazy indiscriminately pulling down whichever data it can decode.
Even with Vista codec packs installed (we used K-Lite) and the .mp4 reg hack which supposedly enables MP4 file indexing in WMP11, we could still only jam more "traditional" WMP-capable media into the library (MPG, AVI, etc.). Even then we could only manage to stream old school MPEG-1 video to the PS3. We're sure if our Vista machine would add our PS3-compatible H.264 encoded movies to the library that would be a different story, but unfortunately that's not the case, so we hit a wall.
Tried though we might with other DLNA media hosts (like Connect 360 and TwonkyMedia on the Mac) we just couldn't interface the PS3 with our H.264 video library, patiently lying in wait. It did spot our two Sonos units, but it couldn't do much with them. Eventually our attention turned to the video upscaling, however, and we we weren't disappointed; the visual difference seemed immediately apparent when popping in God of War II. (Unfortunately our pictures didn't do a fantastic job of illustrating that, but hey, check it out for yourself.)
So, anyone having better luck with playing back network video on your PS3? Drop us a line in comments, we're open to suggestion here.