Hi,
I just got HD recording working through cablebox-->firewire-->sage.  It works quite well.  I'm having an issue with playback on certain channel content (for example, the NCAA finals last night).  Similar to this thread here:  
http://forums.sagetv.com/forums/showthread.php?t=16003&highlight=choppy
and this:
http://forums.sagetv.com/forums/showthread.php?t=16207
I'm currently using NVIDIA purevideo decoder, VMR9, FSE enabled on a Geforce 6200.  When I play using WMP, the picture is smooth (I have VMR enabled, overlays UNCHECKED, high quality mode UNCHECKED).  CPU usage is only around 50%.  
So I'm wondering why playing through WMP the picture is smooth, but through Sage the picture is choppy.  I'm 99% sure that I'm using the same decoder (nvidia) with the same settings.  I tried disabling FSE and 3D Acceleration with the same problem.
Oh, and I'm using SageTV 4.1.3 on a A64 3000+ s754/1GB RAM.  Running in service mode, but also running sage UI from the same machine.  Hmmm maybe that has something to do with it?  Are there some buffers I need to increase or something like that?
Thanks,
E