monitoring kids Internet activities

My teen son and tween daughter spend a lot of time online and like most parents, I have my concerns. We have some rules, we try to educate them and share our concerns...generally keep the line of communication open like anything else. But I'm not sure it's enough in this technology age - it's tough keeping up with them and what they're possibly getting into online, especially as their curiosity, interest in social interaction, and peer pressure all grow, at times ahead of their development of good judgment and awareness of ramifications.

I've recently installed monitoring software - Family Cyber Alert - that will allow us to better keep tabs on their PC activity and hopefully better be able to know what's what, what we need to learn more about, what else we need to caution and teach them about...and ultimately help them stay away from potential cyber-related trouble.

It looks like a great product to me, something to give me an added tool to better guide and educate my kids, and possibly keep them a bit safer in the process.

From the feedback I've gotten from a few friends, including two others that use this software, it would appear that there is strong debate about whether parents should let their kids know they are using this software. I'm curious what experience others have with this concern and this type software. Any thoughts, experiences to share? Thanks!