I would also say that in practical terms, if the limit is 4 HD shows at once (I think ours is 4 HD + 1 SD tuner), I can't always count on more than 2 shows recording at a time. Because the time is off, most shows get clipped at the end (it feels like a lot though I suspect it's <30sec but sometimes it's important). So all our recordings are set to end +5min (there's nothing shorter), which means if we are recording shows on 2 channels followed by shows on 2 other channels, all 4 HD tuners are tied up. In the past I've had to recording a third show in SD, though that's only possible when the conflict exists at time of recording.
This is still better than Rogers I think, which is incapable of recording the same station on 2 tuners at the same time (I think the Fibe PVR can do that). So if I have an 8-830 show and an 830-9 show recording on the same channel with +5min on each, I get 8-830 and 830-905 with a few seconds' gap in between (often the very very end of the first show is still on the start of the second).
I assume there's nothing to be done about the time thing, which could be the broadcasters' fault for all I know.