Clipless Pedals - Yay or Nay?

I'd you haven't already, I'd suggest trying clips on your trail bike first and gaining some familiarity with them in different terrain. When you're in full on DH territory the last thing you want to worry about is your feet.

When I switched to clips, I did so on trails I was already familiar with as I knew what to expect terrain wise. For a while afterwards whenever I rode new areas I switched back to flats. I was worried about unclipping in time, but it wasn't until I had an off and had unclipped without even realising that I stayed on clips permanently.

Both have their advantages. Since I am not racing at the top of the standings, I prefer flats for DH and Enduro races as well as general riding for the fun, the confidence and the good habits they teach me.
Mind that most pros who regularly use clips spend at least a portion of the off-season on flats to get rid of bad habits, technique-wise, that may form over time if you consistently ride only clips.

I normally go with flats on the DH bike and clips on the enduro. I ran clips on the DH for several years and was fine with it but after a big crash with a few months out with a surgery (non-related to using clips) around 6 years ago I got back on the DH bike slowly after that and opted for starting with flats and I never really got back to clips since.
I just love the freedom and confidence on the turns and with a good pedal and some Five Tens I never had any trouble on the rough stuff.
On the Enduro bike on the other hand I prefer clips because of all the pedalling involved.

Clipless always cross country and riding the shore makes no difference clipless are the way to go.