I found a problem when running a multi currency environment:
in the file module/payment/google.php , when building the order XML, we'll have something like:

info['currency'] . '">' . $value['final_price']

Now, see this case:
1. my store's default Currency is USD
2. EUR is also available

My customers is shopping in EUR, so $order->info['currency'] == EUR
but the $value['final_price'] of the object order is set in USD

which means we are outputting the wrong couple.

So, either we write USD on the currency, or we translate the price into the selected currency.
(besides the fact that outputting a price in a currency different then the registered one (in my case USD) would give trouble to most of users.

Please advice