Azores Airlines is a safe airline where, if all goes to plan and no complication arises, you'll have a good flight with some food and decent, if probably old, seats.
However, the airline is also ranked one of the worst in the world for customer service, largely because of their disdain for customers if anything goes wrong (such as delays or flight cancellations).
My own experience didn't even require anything to go wrong. All it took was a variation from bog standard cases.
As I was moving to the Azores for the medium to long term, I travelled with a lot of luggage. Some time before the flight I looked through the website to work out how much this would cost me, and found that it was actually cheaper to buy a second ticket than to pay for the equivalent extra hold luggage. This was true for both legs of my trip - British Airways to Lisbon and Azores Airlines to Faial. So I bought second tickets for both legs, looking forward to have empty seats next to me, as well as making modest savings on the price of the extra luggage.
BA handled this well. They were obviously a bit surprised by my approach, but check in staff communicated with gate staff and cabin crew to handle passenger counts and even though my solution wasn't what they were used to, it all went well enough.
The next day, at the Azores Airlines check-in desk, things did not go well. Staff were surprised, but refused to accept my solution. Instead, they cancelled my second booking and charged me for the extra luggage. I asked them repeatedly to explain to me why, and show me the terms and conditions (which I had checked prior to booking) to point out which rule I had broken, but they were unable to do so because everything I had done was perfectly legal, within the rules. Not only that, but their cancellation of my second ticket was not justifiable by their own terms. And, as they pointed out very assertively, I had booked a fare that didn't allow for refunds - so they kept the money I had paid and then took even more money off me for the suitcase.
Talking to Azores Airlines staff is a bit like arguing with a brick wall. It doesn't matter if they are in the wrong, or if you have in writing what your rights are: they switch into an authoritarian school teacher mode and will simply not reply to your points or questions. Another example: if you book a Business ("Comfort") Class ticket, you are promised to be able to make "free" changes or cancellations. If, however, you try to do so, you will suddenly find that staff refuse to make any change unless you pay an "admin fee" which isn't mentioned anywhere on their website. Showing them screenshots, booking confirmations, their own website's terms and conditions won't make a difference.
Ultimately, Azores Airlines has a broken internal culture. Whatever internal guidance there is, it is incomplete (not anticipating every scenario), and out of sync with the information presented to passengers when they book their tickets. It may even be out of sync with the law, based on how passengers experiencing delays and cancellations have been treated. However, airline staff will rigidly apply whichever internal processes they deem suitable, whether or not it breaks contracts or the law, and whether or not it shafts customers.
If you travel to the Azores, my recommendation is to use TAP or Ryanair from mainland Portugal and avoid Azores Airlines if you can.