Daft thing is they have one rate when you are paying and then another when you are transfering into you account - and surprisingly enough both are in their favour.
For smaller deals it is no so relevant but certainly with larger deals then it is worth doing a dry run first rather than going by the Google exchange rates
This is annoyed me as i was happy with the final sum until i paid via paypal and it cost me just over £100 more than expected, glad it has free shipping