Not everyone has Sky or Virgin, and many companies are bringing out Freeview PVRs so I can see this being pretty popular, I definitely want one.
@ aiphanes: "its unknown why that fan test does not work in the 60 GB."
No it's not, it was clearly added as some kind of hardware feature in the 40GB and later models.
I really wouldn't risk doing this, regardless of how infrequently you do it, as a good amount of heat must be building up inside there to make the fan hit top speed in such a short amount of time and we don't know how much punishment the hardware can take (lets face it, the 360 can melt ...
It's not hard to work out really, it's:
0 hours:5 mins:24 seconds:0 frames (it's more likely to be frames than milliseconds)