First, CHX did not simply died. It was swallowed by another company, evolved into a corporate product with all the bells and whistles which in turn was swallowed by an even bigger corporation and still lives as part of an enterprise business product, a module that probably nobody knows about. But payload filtering was, in my opinion, the greatest feature of CHX and it did and still does run perfectly fine today (I'm still running it in my XP machine). I'm not sure about the other firewalls out-there, but is definitely one of the few that can alter the TCP traffic with variable-length data and operate on the stream in transit (ex. gateway).