I'm just coming back from an abortive experiment with Things, and I think the advantageous element in Things' Today view is that actions that are scheduled to begin 'today' will automatically show up in the view. As Craig noted, you can accomplish this in OmniFocus by flagging everything that starts today and then using a 'flagged' perspective (or I suppose you could simply set 'today' as a start date for everything you want to flag). However, the simplicity of Things' implementation is definitely superior, including the ability to click 'Not Today' and have the item return to its previous state (i.e. its original set of attributes).
I guess The Hit List will introduce yet another blend of arrangements to this increasingly crowded space.