We just implemented the Select widget, and its a great addition. The only suggestion I have is to synchronize the layers available to select from with those that are currently turned on. If you're working with a map containing many layers it can be cumbersome turning on/off the layer(s) in the Layer List then finding the same layer(s) the turn on/off in the select widget. Having the list in the Select widget already pared down to only match layers turned on in the Layer List would make it that much smoother.
I saw the Attribute Table widget has an option to sync with layer visibilities - not sure if that means whether a layer is turned on, or if that refers to any scale dependencies, but either way I liked the notion (see attached).