Here's a suggestion:
Have HTC give people that have mirrors the file and have them set it up on their ends.
When released, Add a link to the mirrors IN THE ANNOUNCEMENT FORUMS. This will guarantee that most of us will use the mirrors instead of the HTC server.
Fileplanet is also a great idea.
This way we can avoid the "ohshit its out" and everyone downloading the thing and those that have the mirrors will also be stuck with the extremely slow downloads before they can put it up in their mirrors.
You cannot prepare for the unknown, but you can prepare to be surprised!