Sounds like good stuff, but why will it get rid of our dependency on oil? For that we should be growing rapeseed.
[edit] I haven't heard much about the downsides of hemp. According to the mighty Wikipedia it "rots easily from the inside out, and was superceded not only by cotton but wool, sisal and jute". I don't know much about this myself so would be interested to hear what others think. Interesting thread.