With 10d I had some problems rendering two small videos I should show during the weekend... it kept blocking at the same place over and over with "low memory" error message
Then I installed 11 and after a false start, it kept rendering and rendering... now I have mpeg2 for DVD and full hd ready for "media player" playback...
My workstations has a CUDA enabled video card but the drivers are old and it is not possible to enable it.
Later, at home, I will try to downconvert the full hd 50i to 720 25p for tablet playback with handbrake