There are few problems with the plasma widget dashboard currently in KDE.4.9.3. Reviewing discussions I find that at least the first I will mention has existed in previous versions and remains unresolved.

1. If the user has their panel at the top of the screen then the "Widget Dashboard" icon will not allow an exit. Clicking on it has no effect. It will work if the dashboard has been opened and then the widget dashboard icon is clicked BEFORE anything else on the dashboard. Additionally, if the News widget is open on the dashboard and a link on it is clicked to open in a browser window and the user then clicks the widget dashboard icon it will exit to the desktop. So the problem seems to be related to focus.
It would surely be desirable to be able to configure the dashboard so that the exit icon could be moved to the bottom or the side of the screen - or at least have the bug fixed so that it works regardless of where it is placed.

2. Choosing "Desktop Dashboard Settings" has no effect. It should work and the user should be allowed to change the transparency colour and the level of transparency of the Dashboard.

3. I have noticed that the calculator widget (when placed on the dashboard) loses some of its graded rendering after a fresh login. It can be restored by unlocking the widgets and resizing it. This bug appears on all my machines including my laptop - so it is not related to a specific video card. It would be nice if this was fixed.

Otherwise, love the Dashboard. It is particularly useful if "Show an independent Widget Set" is selected under the Worspace/Dashboard setting.

Can you please file a bug report for these issues so it comes to the attention of the developers?
As you mention it has existed in prior versions, please search for a pre-existing bug report before filing a new one.