ActiveWords is one of those tricky products to market. I originally downloaded it on the recommendation of Ernie the Attorney, played with it a bit, and let it languish, after mentioning it on my blog.
And I picked up AW after hearing about it from Jim. ActiveWords and PersonalBrain are the tools that are always running on my machine (along with Outlook). I particularly like the "default" which fires off Google (customizable) for any unrecognized ActiveWord.
Based on the article, I might want to have a look at GuruNet as well.