I had been waiting for contactless to be confirmed before paying Luton DART a visit. Today I got the bus over from Stevenage and tried the DART from Luton Parkway to the airport (just one way). The gatelines do indeed now have the familiar yellow 'contactless' logo, which worked. I did not spot any signs indicating the fare.
The ride was not rough, but definitely what I would call wobbly. It was a bit like standing on a large inflatable. Constantly making small movements front/back and left/right.
Even with relatively few passengers, there was a queue at the airport exit gateline, at least partially due to faffing. This is also visible on the previously linked video. I am wondering if people are under the impression that the entry gateline is job done and then put away whatever 'ticket' they used there.
My card account is currently showing a pending/uncleared transaction "Tfl Travel Charge +£0.00". I am familiar with the use of initial zero value authorisations, but was not expecting TfL. For clarity, the only gatelines I presented this card to today were DART.