Just finished my downstream O2 sensors on my 2013 EcoBoost Limited, super easy.
Once I got the car up and on jack stands, and removed the lower air deflector, it took 5 minutes to get the bank 2 sensor off, another 5 minutes to restinstall it, the rear sensor bank 1 was a little more work but still easy to access, the hardest part was getting my hand up into the small area to un-clip the connector, the heat from the tranny made it difficult.
So anecdotally, I'd have to say, at least on the EcoBoost cars, O2s are relatively easy.
Once I got the car up and on jack stands, and removed the lower air deflector, it took 5 minutes to get the bank 2 sensor off, another 5 minutes to restinstall it, the rear sensor bank 1 was a little more work but still easy to access, the hardest part was getting my hand up into the small area to un-clip the connector, the heat from the tranny made it difficult.
So anecdotally, I'd have to say, at least on the EcoBoost cars, O2s are relatively easy.