I have downloaded hundreds of 721's before we shipped them out of the Dishstore. We do it for 2 reasons...
#1 To make sure there is no issues with the receiver rebooting for an hour and then having angry customers calling the office complaining we sold them a defective unit and demand some sort of compansation or a replacement unit to be shipped out to them.
#2 To help prevent Piracy since Software Version L054 makes the receiver very easy to hack.
But anyways, yes its perfectly normal for the receiver to reboot severl times. A matter of fact I have seen receivers reboot for up to an hour before the Point Dish screen will finally come up.
Best thing to do is leave the satellite feed connected while waiting for it to boot correctly, however if you do disconnect it, I have found it boots up faster but then you run the risk of it rebooting when you screw in the satellite feeds.
But I don't know what it is, but the unit is stable after the initial software download.
Other than that, any unit shipped with a yellow card is not on L054 which means the units are stable out of the box and will function properly without taking the initial software download.