WYTWOLF  The done button is there, but it's of to the right of the widget. The issue I have is that text no longer works, and the 7th day forecast (picture) is wrapped around and down where the current day temperature is. It covers the temp.  
(Version 3.4)

ANONYMOUS  The station preferences are per-instance and not per-widget because many people are using the widget to monitor several stations at the same time. That means that every time you update you instantiate a fresh widget and the preferences for the old one are lost. It's a small price to pay for functionality. The widget is usually quite static and updates are few and far between, but in this case an update was necessary to add the new 7-day forecasts from Environment Canada.

The missing "done" button is a well-known issue with dashboard: since switching to 7-day forecast caused a resize of the widget, installing over the old one didn't unload the css properly and left it in a mangled state. All one had to do is hit apple+R while mousing over the widget to get it fixed. There's a note on the widget's website to that effect, but unfortunately it didn't make it elsewhere.

I'm sorry for your troubles.  
(Version 3.7)

HELIKING  Works fine for me. Done is well highlited as button labelled "DONE"  
(Version 3.8)