Note to users who see ??? Rated 5 out of 5 stars
In case you only get ??? instead of the correct value in your own currency, go to the addon options. You will see that it shows you NaN for all the currency rates, meaning the addon cannot retreive the rates. Luckily, there are TWO sources for the rates to choose from. By default, the standard source is Google. Change it to WebServiceX for all currencies you want to convert and hit update! Looks like google changed something - but the rates can still be received via WebServiceX without any problems! Hope that helps anyone having trouble with this!