I bought a RFUSB PRO on ebay for $15. It is a cooper usb controller that uses a customized version of Homeseer. Unfortunately I found out the software cannot be registered and is only good for trial use (per homeseer). That said it has proved useful in figuring this thing out. It does NOT as far as I can tell activate a scene via the scene controller. It makes you think it does by letting click an icon for the controller button in the software and then watch your lights come on. However, after I was able to program my controller via ST it became apparent that Homeseer was only activating what it thought the scene was. It appears that Homeseer is sending the scene activation command directly itself. This agrees with what JD said in his point 1.
I Did want to clarify my earlier point about local scenes not being (fully) supported.
In most Z wave – only platforms, you define a scene on the interface to the primary controller. It keeps track of which devices are assigned to which local scenes and at what levels.
Then you use scene controller configuration to map the buttons on any individual local scene controller device to the pre-defined scenes.
This is the process piece that SmartThings is missing. You may be able to write code to individually send each required zwave scene command set, but there’s no platform management of zwave scenes. Each individual coder has to keep track of them in each individual Smartapp/DTH.
Again my guess, for which I have no data at all 
, is that they chose not to offer built-in standardized UI management of zwave scenes because it would be a feature that was not available for zigbee devices.
Good point. It would be great to see a standardised UI for many of the Z-Wave command classes, mainly all the ones my Z-Wave Tweaker tries to deal with: CONFIGURATION, PROTECTION, SWITCH_ALL, ASSOCIATION, etc…