When my XSAT CDTV 430 is in standby there's no power to the LNBF, so it doesn't matter what the rest of the box is or isn't doing. As expected, there's a delay before getting pictures if it's been on standby for any length of time.

On the other hand, when my UEC DSD 720iF is in standby the LNBF is still powered and the box is still quite warm, suggesting that not much gets shut down. And as expected, if I have my SelecTV card in it instead of my XSAT, pictures are instantaneous when it's taken from standby to "on".