In terms of overall usefulness, I found the site to be better for either stoking or calming fears about chances of admission. Since the profiles are self-reported, it's very possible that you'll run into some obviously fake profiles.
Those outliers aside, the graphs for the schools' different admissions outcomes are pretty amazing in terms of raw data. What's even more impressive is that they span all the way back to the 2003-2004 application cycle, so you can have a pretty clear idea of how admissions decisions have been made for the schools you are interested in applying to.
Also, if you're interested in seeing this data put to an aggregated use, see the posts we have about the law school calculator.