Overall, I felt this interview process was let down by the way it ended, especially considering how much time I had to invest in it. Details:
I was contacted very quickly after applying by a very friendly and professional recruiter who ran through an initial interview with me and explained what I could expect for the rest of the process. I interviewed with four more people - the manager who I would report to and three members of the senior leadership team.
Each interview was one hour long, so with the requisite time preparing for each interview (checking LinkedIn bio's etc) I think I probably invested 8 hours or more in the whole process, over the course of two weeks.
That's one full working day, while of course I continued to work in my existing job full time.
The interviews themselves were enjoyable - the people interviewing me were clearly all very smart, very professional, and took their business and the interviews seriously. There were challenging questions in all of them, but that's par for the course.
Each interview finished very positively and the original HR contact came back to me to confirm the next interview almost immediately.
Unfortunately where I felt disappointed was at the end - the day after the fifth and final interview, I just received an incredibly generic email from the HR contact saying "Thanks for your time but we've decided to go in another direction". I replied to it asking for any more specific feedback but got no response. I found this a really poor way of wrapping things up.
To be clear, I'm not complaining that I didn't get the job - if there was a better candidate than me, that's fair enough. But given the amount of time I'd invested, and the high-touch nature of the process up to that point, I felt that it would have been appropriate to provide something a little more personal, and provide a little more feedback from the people who interviewed me.
So advice to future interviewees - be prepared to invest a lot of time, for potentially just a dismissive "thanks but no thanks" email at the end of it.