Wordtracker's GTrends tool

I apologize if someone's previously posted about this. I came across it a few months ago, lost it (forgot it was Wordtracker's), then finally found it again. :-) Anyway, I was wondering if anyone here has used the tool and whether or not they find it helpful. It appears to be connected to some promotion called the Thirty Day Challenge (not signed up, so I don't know all the details). I've played around with the tool and it seems interesting; I'm just curious about other's experience with it. Here's the link if you need it:

http://freekeywords.wordtracker.com/gtrends/

Thanks,
Deb