I know very little about how law is written, but my impression is that most people who pay attention to it are more concerned about the large ideas than the exact wordings - that's how you have politicians voting on bills when they haven't read every word. How can they when it's thousands of pages long?
So this might be more useful to a small number of politicians and lawyers who are examining law closely, looking for loopholes, or concerned about the exact details of a particular statement's pedigree, but I don't really see the general appeal.
I would rather have a tool which provides similar information, but on a higher level. An independent overview in layman language, general information about how it came about, how it's significant historically or with respect to existing law, and with the option to drill down to the actual language and gritty details. Of course, this would take much more work to build and maintain. I've been a fan of opencongress.org but I've found that switching between opencongress and wikipedia is the most effective way to understand the context and significance of a bill.
Reading the actual text of a law is usually about as useful to me for determining its implications as reading the source code of a printer driver would be to my dad for figuring out how to install a printer.