Based upon the trial, it appears to have some significant bugs. You'll definitely want it to analyze everything twice. The first time around, it said pretty much everything on the Pixies' "Death to the Pixies" album was 10 BPM on the first pass with an unknown beat intensity. The second time around, songs like "Debaser" came out at a much more believable 135/40. I realize the FAQ says something about a 'corrupted iTunes library', but given that this was a fresh playlist, I'm highly doubtful.]
Additionally, if you have a large library (I gave it over 13,000 tracks to chew on) it overestimates tremendously. It started out at 20 hours and a ten minutes later, it is now down to 8 hours. It'd be nice to have a better estimation. Perhaps it is counting the double analysis that you'll have to do?
I'd recommend anyone interested spend some serious quality time with it. Unfortunately, I'm not sure 24 hours is enough for those with large libraries, much less the 13 hours left as of this posting.