two way confusion resolution:
As Chris stated, Z-Wave has alway's been two way technology. With this he means that when the usb/serial controller send's a command it looks for an acknowledgment that the certain device actually recieved the command. This is how the devices have always been two-way.
With the new two way communication (just kidding - trying to confuse you) it is two way at the switch. This mean's that the switch does not need to be polled like the previous version's were. When you change the switch on at the wallplate, the switch sends to the master controller (in my case homeseer) that the switch has changed to ON. Previously homeseer would poll the switch every 300 seconds (or user defined) to see if the device had changed it's state. Now the switch automatically sends the information to homeseer when it happens (immediately).
The best part of this is:
1. You can program events around light switch changes.
2. You can eliminate the CPU intensive polling.
3. Homeseer knows exactly the state of a switch. This helps with programming events based on light conditions i.e. if switch on then do this..... - this limits the potential problems that could occur from such a statement)
The bad news:
I think homeseer is misleading us on the two way implementation. Again, as Chris stated all zwave devices are two way. The ACT ones are in fact two way but they do not transmit local status changes. The newer Leviton, Cooper, and Intermatic switches all transmit local status changes. I could be wrong about the ACT devices, but I looked at their website (ACT HOMEPRO)
and it does not mention anything about local state updates - a feature that surely would be mentioned.