The beauty of the CM15A (and the CM11A before it) is that they were designed to be standalone controllers, that didn't require a PC to be connected all the time. In my case, I keep it connected to a running PC all the time, but I'm not using any of the newer AHP plugins that require AHP to be open 24/7.
It has been just over 7 years since I got my first CM15A (I lost track of what number I'm on right now, it has been replaced a number of times - at no cost to me), but that seems like an eternity (which it almost is, in technology years!).
Migrating over to a laptop-based (or very small PC-based) system, using something like Jeff's XTB-232 or Dave's RR5x5 is a road I'm nervous to head down. I'm a geek, but I've been happy with the simpler, "non-geek" solution that X10 provided with the CM15A and AHP. I know that migrating over to something new will involve buying more stuff (an interface module, an RF transceiver, some sort of computer to run it on, a good UPS for that computer, etc), and spending a lot of time configuring software, testing, and making sure the system is really working properly. I'm just not ready for that.
Maybe at some point in the near future...