I agree with you except with X10 the problem is bi-directional. You actually don’t know if the device received the signal from EZSrve or any other X10 controller and you don’t know if EZSrve saw a message from another X10 controller that actually affected the X10 device but was not received by EZSrve. Looking at an X10 device status display would only be maybe this is the status of the X10 devices. That said, other products like Powerhome do reflect the X10 device status based on X10 messages received as well as X10 messages sent. There is a version 2 of EZSrve coming soon according to the release notes document. Perhaps that version will do what you are looking for.
yes, several commercial products watch the powerline commands that way. it can be quite useful, even if x10 isn’t 100% reliable. i’ve created some relatively complex “macros” on a pc using that paradigm, which unfortunately aren’t possible as yet with the EZSrve firmware. for example, “presence detection” in a room which is covered by two motion detectors in different areas. give the motion detectors the addresses A03 and A04, and a lamp in the room B03. then, the pc (hopefully someday the more power-conservative EZSrve) can be programmed with a macro such as (for turning the lamp on:) “(if A03-ON) OR (A04-ON) is seen then send B03-ON”, and (for turning it back off, and also for turning it off if it has come on for some other reason, like false detection, light switch malfunction, manual operation, etc:) “(if A03-ON hasn’t been seen for >1 minute) AND (if A04-ON hasn’t been seen for >1 minute) then send B03-OFF”. this avoids the automatic “OFF” from the EagleEye or ActiveEye turning off the light while i am still in the room but only visible by one or the other motion detector.