This depends on the particular church. I know that Serbian Orthodox and Russian still officially use the Julian calendar. AFAIK the most of other Orthodox churches like Greek, Romanian, etc. have switched to the Gregorian calendar, e.g. they celebrate Christmas on Dec the 25th, not January the 7th, like Serbs and Russians do (Julian calendar is 13 days behind the Gregorian at the moment).
Even for the Romanian and Greek Orthodox churches, the Easter rarely coincides with the Catholic Easter. You are right about the Christmas though, it is on 25 for both churches.
All Orthodox Churches are still on the Julian Calendar, they've just adopted a version called the Revised Julian Calendar, which moves certain holidays so that they align with the West. The rest of the Calendar, apart from something like Christmas, is still Julian.
