OK, I live in Oklahoma--almost flat, though we do have hills--and I pick up OKC DTV stations better than I do Tulsa DTV stations--Only get three Tulsa stations 60-73 power on my Dish 811, but get all of the OKC stations with 70-96 power on Dish 811--analog stations come in about the same. The thing is, I live 40 miles away from Tulsa, but around 70 miles from OKC. (though I think that has more to do with the 811 than anything else, but don't have another DTV receiver to test my theory.)
And to top it off, i do it with a $39 amplified set-top antenna from Wal-Mart.
Anyways, with this same setup, I've picked up analog stations from Missouri, Texas, and Kansas, for me at least I've found that this happens more often early morning with fog or light clouds. During fall time seems to be the best time for me with this setup to pick up stations from far away.