http://insomnia.ac/hardware/the_fake-hd_era/
I recently got a 26" 1080p-native LCD (the first such display I get -- before this I was mostly using a 720p projector) and hooked it up to my 360, and I am basically 100% certain that even THE FUCKING DASHBOARD is upscaled. The only game I've tried is Ninja Gaiden II, and I am pretty sure that's upscaled too.
I'll also be getting a 37" 768p display soon and setting it up next to the other one, so I'll be able to make some solid side-by-side comparisons, to resolve as many of the issues discussed in this thread as I can.
I should be writing some more hardware articles too.