If it's creditcards only, it depends who you're processing with.
If they work with Korean/Japanese cards and you've got Korean/Japanese sites then you'll do well with the traffic.
Same with Euro countries, if you can bill them and offer content in a lang they understand they will get their cards out, but you've got to be able to take debitcards.
The UK has got nice traffic, but, if you can take debitcards then it becomes twice as good.
A dialer option is always nice to have though.
