Never having ordered from Greenman Gaming before, I can't tell you if you'll have to pay shipping (or if that shipping will get you release-day delivery), but for $34 you can probably stand to wait a day or two after launch. Just be sure to use coupon code "20SUM-MERSA-VINGS".
Update: It uses Steam somehow?! This future is amazing. They're putting futures in my futures.
Order Deus Ex: Human Revolution [GreenmanGaming.com via Dealnews]