I've set up an experiment to test Remarketing and see what I can do.
I was wondering if I can see somewhere in Adwords on which websites in the display network my ads are beeing shown?
If I am not mistaken, when you go to your remarketing campaign, click on Display Network Tab and then select Placements. Now here, under Automatic Placements, you should be able to see the placements from where you are getting the remarketing clicks on your website and whether they are worth or you want to optimize accordingly. For example adding placement exclusions or rather adding them as managed placements if they are really worth in terms of your business.
Parkaj is correct. I would also keep an eye on the view through conversion matric (should you have conversion tracking set up). This is essentially when someone views your ads but doesn't click, comes back to your site and completes your conversion action.
I have worked on acocunts which have had high numbers of view through conversions and although it may be difficult to guage how much of an effect the view of your ad has had in persuadinga user to convert, it is still something that should be takenm into consideration.