Herdfan,
As far as linking, there are Z-Wave switches that are only responders. The ones that can control other switches are sometimes called transmitters. So the answer is that not all devices can control other devices. I have a house full of 'responder only' switches and am fairly happy. I am waiting for a multi button keypad type 'controller' wall switch to become available, I have a place where one is needed.
In a very basic system, devices can be included or deleted from a Z-Wave network only by the master controller. The master is just the first controller that you use and is necessarily a hand held unit. During the inclusion or removal of devices the controller needs to be within a few feet of the remote devices (security feature). The network database can then be copied to other 'secondary' controllers. I'm guessing having only one master controller makes the routing table easier to manage.
An example of setting up a link on a controller is something like - press the control buttons once to select, hold the include button, then press the switch on the remote device and select the desired 'on level', release the include button and the link is made. I do not know of any current software that will manage the links in the controllers. I suspect that something like that may be in the works though.
I miss the link 'everything to everything' ability that INSTEON has. The newer Z-Wave switches will probably have a similar feature available. It just isn't on all switches at the moment. I have had Z-Wave installed in my house for five months and have not had to replace any in that time. The Z-Wave switches are more expensive than INSTEON, but the reliability and longer warranty make them a better value in my mind. Also, having a choice of manufacturers is nice. I think competition helps drive quality up.
Z-Wave has battery remotes available that can store and run timers without any PC required. I find that feature, and the fact that small battery remotes are available, enough to overcome the current limited linking ability. Z-Wave also has motion detectors available. The software to manage them is still in the works but there are hardware devices that can be used. You would want to investigate what model of controller will set up a detector prior to buying any. Some controllers have more options than others.
Ken