Point-in-time legislative systems such as you describe exist elsewhere -- with notable open-access collections that have them in Canada and Australia. The first was developed in Tasmania some years ago (Google "Tasmania EnAct" to find information about it).

I'm not sure that diffs would do much to increase understanding, as they tend to operate at way too granular a level for people who just want to understand what the damn thing does. Sorta like trying to gauge the purpose and effects of a good-sized piece of software by reading a patch file. Not in my skill set, anyway.

The section-by-section Notes that accompany the United States Code provide a change history in narrative form. The Notes for a particular favorite of mine, the Wild Horse Annie Act, are here : http://bit.ly/ivW2b . Another interesting document tracking the evolution of the law, still more accessible to read, is the Annotated Constitution of the United States, one version of which is here: http://www.law.cornell.edu/anncon/html/index.html

Here's what we WON'T see in the wake of this invention:

-- Nailed-together case mods.
-- Trade press articles about whether or not Microsoft/Google can withstand the competitive onslaught of this new nailing technology.
-- Trade press articles about whether or not Microsoft/Google is going to buy the manufacturer of this new nailing technology.
-- Trade press articles about whether or not Microsoft/Google is going to buy the inventor of this new nailing technology.
-- Any product called the "iPod HurriQuake".
-- A Sharper Image catalog in which every third item is a so-called "HurriQuake accessory", and is a stuffed animal that lights up.
-- An HCSE ("Hurriquake Certified Structural Engineer") program, in which Bostitch tries to scare every construction company in the country into paying a zillion dollars so their carpenters can be "certified".
-- The National Association of Realtors running a national "HurriQuake Inside" TV ad campaign (sound sting: four hammer blows, different pitches)
-- A mad scramble on the part of hammer manufacturers to market their products as "HurriQuake compatible".
-- Any TV spots that begin with a 3/4-body two-shot of two guys saying, respectively, "I'm a HurriQuake" and "I'm a screw" (costuming left to the imagination).
-- Any youthful you're-such-a-rebel, pushing-the-bounds-of-taste YouTube offerings involving HurriQuakes, Roman centurion costumes, and Mel Gibson.
-- Any book entitled "Head Rush HurriQuake"
-- Any book entitled "Enterprise Fastening Strategies"
-- Any book entitled "Nailing down the HurriQuake" with a Victorian engraving of a hammerhead shark on the cover.
-- Walter What's-His-Butt from the Wall Street Journal bellyaching that nails are still too hard to drive and how he hits his fingers all the time and how unrealistic it is for the construction industry to expect people to live in houses if they can't come up with a nail that's easier to use.

Outside the tech sector the noise levels are lower, I'm tellin' ya.