Datapoint.
Had two OS flights less than three weeks ago. Recieved email on the flight day morning that first flight would be delayed 50 minutes due to the operational reasons.
Incoming flight arrived ahead of schedule. Contacted OS by phone and at the airport check-in counter to rebook but there were no same day availability on my chosen route.
Missed connecting flight in VIE. At the transit counter I chosed rebooking to other airline(not Star Alliance) and was asked would I go to lounge or they give me 15€ f&b voucher and also business card for EU261 claim contact detail. I chose OS lounge, did not care 15€ f&b voucher which OS should give me anyway and csr called to lounge to let them know that I am coming, used OS flight issued boarding pass to enter from the flight already departed. The new flight scheduled arriving time was 3h45 after originally booked, so EU261/2004 applied.
Made a claim a week after the flight. Received a case number 8 days after the claim. On 9th day, received an email that there is extraordinary high volume of incoming request and it takes time to response.
One day after recived an email asking my bank account details with note that a request for documents is no entitlement to compensation.
After the details were sent, got response in less than 30 minutes that claim was approved and forwarded to accounting department. Takes up to three weeks to get the compensation to the bank account.
Important note: I did not wrote my M&M account number to the claim form, so the procedure and speed should not affiliated with M&M status.