Not quite sure why you would want to do this, but AndroidCentral.com offers a video tutorial on how to disable the TouchWiz interface on your brand new Epic. Their quote:
Yeah, you can turn off Touchwiz on the Sprint Epic 4G and get rid of the static home screen icons and horizontal launcher. But what you're left with isn't really an improvement. You're stuck with three home screens, an outdated launcher, and a feeling of guilt for not listening to us in the first place.