Seems like a good idea; has some issues Rated 3 out of 5 stars
I found two gotchas in my brief trial.
1) Extensions that modify pages may cause the WAVE toolbar to report accessibility issues that have nothing to do with the page you're trying to assess. When I encountered this with Link Alert, the summary line indicated that there were errors in the page, but I couldn't find any error icons in the page, even when I disabled styles.
2) "Structure/Order," Text-only," and "Outline" page transformations apparently remove event handlers established in script under some circumstances. "Reset Page" does not restore the original functionality, and sometimes actually causes the problem.
I think working around the first issue is up to the user, unless the author of the offending extension is motivated and able to correct the problem. The second issue looks to me like it's squarely in the WAVE toolbar authors' court.