In reply to Trangia:
The whole point is they're not meant to be transferable/reusable.
> It explains why a French friend was forced at the border to affix the vignette to the inside of his windscreen. They wouldn't allow him to just hold it against the screen. The adhesive is so strong you can't re-use it on another car (in this case his wife's car!)
Also you aren't forced to buy one to enter Switzerland, only to use the motorway network. If you stay off the motorways you can drive around without one (but this is often more hassle than its worth so I'd recommend getting one).
They're a pain to get off but I found the easiest way is to use a plastic disposable razor and scrape them off from the inside. We get one every year and it was getting a bit silly with five in a row so I did some research.
As to the OP, we had two sets of friends visit us here in France in the summer who came via Geneva and hired cars on the Swiss side. They didn't experience any problems taking the cars out of the country (and more importantly, returning them).