It was quick and easy last year about this time. The visa windows are just before passport control. No photos or paper work is required, just hand over your passport and $20 and in a few seconds the clerk will return your passport and the visa stamp, then get into the passport control line. Several people in our group got their visa on arrival and I didn't hear about any having a problem.
Check the cost to insure that it hasn't changed. If it's still $20, have the right amount to avoid waiting for change.
There were other posts about the visa on the Europe forum.
Turkey is beautiful, you'll have a wonderful time.