You don't need root. EP1W writes over everything through odin. Phone isn't even "booted" when it's flashed.
I waited for a while, and gave in before lunch today. WOW this thing is fast, eliminates the home screen redraw lag, and I've been streaming without any "hiccups" for quite a while. That hiccup used to bug the heck out of me.
Showed EP1W to a friend with a charge, he played with it for about 15 seconds and asked if I could flash his. He's been loving it all day!
I'm talking about the "bloated" version, apparently there are some TW4 issues on the non-bloated.