I guess I should add my 2 cents here.
I have used BartsPE with and without the DriverPack and the load times are slow with the DriverPacks. I am not quite sure whether the DriverPack slows it down, but my feeling is that it does.
Most of the time it has been in conjunction with TrueImage and perhaps the other driverpacks are not need on that disk in particular.
There is a case for restricting the supported list for new hardware, perhaps Vista capable hardware it that would speed up load times, but that is really for the admin himself, not the DriverPacks team