You're definitely not the only one.

Here's a question though: in a workplace with lots of space that's able to offer a choice of a small private office or a well-set-up desk in an open office for every developer, would you still choose the open space? And would you be comfortable seeing people who are junior to you disappearing into private offices?

You may well be :)

Personally, I find it extremely difficult to concentrate with music playing. It may be because I'm a musician, but (with a couple of exceptions) it just draws my attention from whatever it is I'm doing.

I think it very much depends on the open office. At my current office we have open offices, but with good sized desks, only 8-16 people in each open area, and plenty of screens and book cases to act as barriers between groups and desks and block out much of the visual 'noise'. We also have plenty of small rooms where people can go to talk on the phone or have meetings. I think this is absolutely fine and honestly don't think I'd work better in a private office.

I've also been in offices where they had 40-60 people in each open area, desk space just barely wide enough for a keyboard and mouse and no dividers between desks and no closed off meeting spaces. Working is such an environment was, let's say, much more of challenge

I've worked in places with open offices that have a no-headphone policy, so I was pretty scuppered in this regard.

Me too. The vibrancy makes me feel less lethargic.