Well, I landed, and the experience has been mixed.
Normally a macOS upgrade only brings new interesting, or useful things.
This is the first macOS update a long time that has literally taken stuff away. Similar to the upgrade from 68K to PowerPC and then PowerPC to Intel chip sets the death of 32-bit applications meant I had to ditch the accounting package that I had been using for over 20 years. Yes, I migrated the data, but it was sad to see it go. It wasn't supported anymore and hadn't been updated since 2007, but it did more than any other alternative package available on the market does so why change, until I was forced.
Other things like my favorite FTP Product didn't matter so much. I can switch.
But what were Apple thinking. They seem intent on making macOS as close to iOS as they can, in a bad way. iOS by its very nature has to have a simpler & less powerful interface than the macOS version. You are limited by screen estate, you don't have a real keyboard (for most users) or a mouse (for most users).
macOS Mail has suffered from the iOS treatment. All the power is generally there, except for the view of mail messages in your mailbox. You could choose which columns you wanted displayed, in which order from left to right & how wide. You could click on the headings to change the order etc. You could have different settings for different mailboxes / folders, just like every other e-mail product for the last 20 years.
Not now. Now Apple decides which columns, in which order and which width with a single popup to choose how you want things sorted. NO NO NO NO NO. This is NOT a good interface, and is definitely not a Pro interface. This is iOS Mail on macOS and it needs to stop!
You can probably tell I am very passionate about this. I do e-mail, I do a lot of it. I stuck with AppleMail because it had enough features for me to like it, it had the multi-column view that I wanted and many "modern" e-mail products didn't support and is tightly integrated into the OS.
Looks like I'm going to have to move to PostBox if Apple are unwilling to fix this, which would be very very annoying. I really don't want to do this.
I want my old Mail View back Apple, why did you do something so dumb. Do you even know how your users use your products, I'm serious wondering if you actually do.