So far, my O day has been really consistant, so I'm going to say waiting to test. I get so impatient & I can't go buy a test until the day I can test (or I WILL POAS even if its too soon).
The only thing stressful about waiting to O is DH's crazy schedule. Like this month, if I O on time, the closest we'll be able to BD is 2 days before O. Well, unless I leave work early & ambush him.