I've been using CB since version 3. It worked as advertised - blocked the sites I wanted blocked. I have a small issue with X4 on my son's PPC using most of the CPU cycles, but killing the process and restarting usually fixed that.

When X5 came out I bought it immediately. They cleaned up the gui. Unfortunately, they also killed the ability to handle network clients (users with their home directory on another machine). This made the product completely unusable for me because my kids all have network accounts. I called tech support and their response was that they never "officially" supported network accounts. I finally got hold of a marketing person and tried stressing how important that feature was.

I did get a refund.

I've tried every new update since X5 came out and they still don't support network clients reliably. I discovered in my test of 10.5.4 that a PPC iMac wasn't blocking anything. I uninstalled and reinstalled twice and still couldn't get it to function properly. I don't trust X5 and will be sticking with X4 for the foreseeable future.