The process itself was handled professionally. Good, timely contact from the recruiters, one interview had to be rescheduled but was done quickly, and when I didn't get an offer I received a phone call to let me know. That was appreciated.
That all being said, this was 3 rounds of interviews, with a total of 8 interviews. Each round was predicated on passing the previous round. The final round was with someone quite senior. If they progressed me that far, you would that the interviews went generally well and I was at least a competitive candidate. I was understanding when I didn't receive an offer, but asked for some feedback on how to improve. I was told they couldn't share any. They seemed like they gave the role to someone else, but then I see constant new postings of the same or similar roles (and I shared that I would be flexible in find a role that was a good fit).
So while the process itself was professional, at the end of the day I don't feel like I was respected as a candidate and wouldn't recommend interviewing with this company without clear expectations of at the very least receiving feedback at the end.