My understanding is that this was the most high risk stage of the commissioning. The team are breathing a big sigh of relief. I believe multiple failures happed during testing the unfolding of the sun shield on the ground, including it tearing, resulting in multiple delays.
Fingers crossed for the next few days while they unfold the mirrors!
Here is the mission control broadcast for the final stages of the sunshield deployment: https://www.youtube.com/watch?v=IBPNi7uGgWM
A lot more information and happy faces
Have been following the Webb blog ever since the 25th, but come to think of it, this would have been a better link:
https://www.nasa.gov/press-release/sunshield-successfully-de...
TL;DR 139/178 release mechanisms have worked flawlessly!