Hi Ray,
If you opted to use event disable, you should consider what impact if any the iRule would have on clients who might connect to the VIP via the same proxy. Those clients may make multiple HTTP requests over the same TCP connection. If you disable all iRules on the TCP connection, you should force LTM to close the connection to prevent subsequent HTTP requests on that connection from not being processed by your iRule(s).
It would probably be cleaner to set a flag at the beginning of each HTTP request and check that before trying to issue a redirect:
Multiple redirect/respond invocations not allowed
http://devcentral.f5.com/Default.aspx?tabid=53&forumid=5&tpage=1&view=topic&postid=17663
Aaron