Are E26 and E27 Light bulb bases interchangeable?

The E26 is the standard 120 volt American base. The E27 is the European variant and is rated at 220 volts. The E26 is 26 mm and the E27 is 27 mm diameter. Everything I have found suggests that they should be interchangeable except for the voltage rating. The small difference in size doesn't seem to be important as some use the E26/E27 designation.