I experience this issue every time I go to seek a pre-Windows Vista driver for an Asus motherboard: their download servers always peter out at about 100KB/s, regardless of which mirror I choose. I have half a mind to set up mirrors of the most popular drivers – even if a LAN or audio driver isn’t necessarily the latest version, it’ll still help people get up and running sooner rather than later.
nVidia and ATI have persistently fast download speeds, even for the size of their respective driver suites. It’s just the motherboard and chipset manufacturers that have this problem. I recall waiting for a 4KB/s download from an audio chip manufacturer because nobody else had the right drivers.
Build it in to the cost of your high-end products if needed. I’m sure the people buying “gamer edition” motherboards, who are the ones updating their BIOS weekly and wasting time asking technical support about how to overclock their RAM and set unsupported timings, should be shouldering the cost. I just like to have drivers available and at fast download speeds when I need them.