A good RF remote will be much cheaper and just as reliable as RS232. The main reason high-end users typically opt for RS232 is for the 2-way communication, not necessarily stability, although you'll certainly get that. But since the interface from the remote to the serial device is still IR or RF, you're not really gaining much over RF alone in terms of reliability. If you don't have any need for feedback (for volume display, confirmation of power and input states, etc.), RS232 is unnecessary IMO for the average user. If you have a high-end, professionally integrated system then that's a different story. I can't quite tell where you're coming from.
If I were looking to make a system more reliable, I'd start by finding all the discrete power and input codes for my devices and re-write my macros using those. Then take advantage of any auto-sensing your HDMI switch can do so you won't ever need to send commands to it (assuming you don't have a matrix switch). Next, consider taking advantage of HDMI CEC so you can get by with sending commands to fewer devices via IR. If those steps aren't enough, then invest in an RF remote which you can use on an RS232 system down the road if you want to take advantage of the feedback you get from serial devices.