Lonny,

The rs232 ports you are seeing on residential gear is there for a variety of reasons. Control of the equipment with a robust control system or firmware upgrades or as a service port for the repair tech. Plain and simple, if you want to utilize the serial protocol for a piece of gear you will need some way to interface with that gear. Creston/AMX/Elan are the top three options for most dealers, as they are market tested, tried and true. There are other ways, PC control is one option, build your own control system or the Xantech IR/RS232 converter. The Xantech piece will make the most sense for you at this point if you are not a dealer for one(or more) of the big three. Serial communications and TCP/IP communications are becoming more of a standard on resi gear and that trend will continue. Why? I think it is because the better manufacturers see the need and want to be known as a company that 'looks out for the integrator'. Many of the people here on this forum install and program control systems and I am willing to bet that the guys that are doing the programming have 'favorites' in there companies product line card, because they are easy to integrate and have a simple robust serial/IP protocol. I know I have my favs. I have seen a lot in this post about how serial is a 2 way communication, they are right and wrong. I have controlled many units that dont give any feedback, do I do these IR at that point? NO. I know that if I screw a DB9 connector to the back of a piece of gear it will not 'just fall off', like an emitter. I have also found that some gear does not have discrete IR commands but will have those needed commands in the serial protocol manual.
If I understand IR correctly, IR is simply a type of serial data that originates as an electrical signal, then converted to IR light energy, transmitted to an IR receiver where it is converted back to electrical energy and then interpreted by a microprocessor for control of a piece of gear. Serial communications stays completly in the electrical domain from one piece of gear to another. We, as A/V people, know that the fewer 'conversions' you have in a audio or video signal the purer the end result, right? Why do we treat control any differently?

Just my $.10