This is the STUPIDEST solution ever, I tried it in a last moment of despiration before returning my PVR-150.,
I downloaded the drivers for the PVR-250 and forcefully installed them for the PVR-150. Voila, it works. I'm not kidding. Before to capture video from my PVR-150, it would crash if I directly streamed video unless I told it to transcode itself. The CPU usage would be in the 50-70% range. With the 250 drivers in, the usage is 10-15%, and that's having one instance decoding a stream from another instance as part of the test. The machine is SURELY not transcoding video.
So for YEARS it seems (I read a lot of back posts for getting the 150 to run in Windows and offer hardware encoding for VLC) no one has figured this out, but that's it. Install the PVR250 drivers and force the 150 to use them.
I would like to know if someone can replicate my results. I'm using an OEM PVR150 MCE without remote and full width version and this set of drivershttp://hauppauge.lightpath.net/software/pvr250/pvr250_driver_118_23257.zip
It seems to work, but I Havn't tested the STOCK apps like WinTV2000 or anything, since I care little for them functioning.