I've been using 7-11/Seven Bank machines more often than anything else... This has made using a foreign card MUCH easier in Japan. I've NOT had my credit union in the US charge me for it's use and I've not seen a supplemental charge - may just be my credit union.

Citibank machines are far and few between and Post office machines are OK but in a bind hard to find (plus a lot of the post offices I've been in have the older machines with the 20 year old ATM's that are not easy to navigate)