I have not tried CNET Tech Tracker, but I was a subscriber to the former VersionTracker Pro (VTP), (owned by CNET). My results:

1. They are great in taking your money. The default for a 1-year subscription is to automatically renew (with a consequent billing to one’s credit card).
2. When I sent emails to express a false positives or negatives or ask for help, I always got the same computer generated reply. When I continued to pursue the matter, I received a real message promising that my problem would be looked in to. Then 30 days later I would follow up to the person who promised he would personally resolve the issue, and you guessed it, another computer generated reply. This scenario occurred several times, perhaps 6 times over a 2-year period. Eventually, I just quit wasting my time and quit berating myself for throwing money away.

In place of VTP, I have happily begun using AppUpdate (donation ware): http://gkaindl.com/software/app-update It is a Dashboard Widget that, IMNHO, does what VTP was supposed to do. The interface is not as polished and some features are missing, but operationally, it's as advertised. Should you choose, it will simultaneously check for updates on VT, MacUpdate, and Apple, checks for updates manually or automatically (daily or weekly), etc. Works with 10.6.1 and is grief free.