Tahoe is not ready. It doesn't have feature parity with Sequoia. It's 2 steps forward, 2 steps back.

I'm on a Dec 2020 M1 Air (8/256).

On September 29th I updated from 15.7.1 to 26.0.1.

For this, I clean installed macOS 26.0.1 using a USB installer after erasing Macintosh HD and I didn't restore from a backup.

Immediate impressions:

1. The new look, it's adorable and merry, "feels modern". It's still flat design but with Liquid Glass.
2. The new very rounded corners, I'm neutral on them. Though they look weird on the 90° corners of my M1 Air. Maybe they look better on t he rounded corners of the M4 Air.
3. Increased padding in many places. Welp.
4. Is the menu bar thicker? It feels like it is.
5. The volume adjust pop-up is no longer in your face.
6. Total free space post clean install has reduced. Went from around 216~GB in macOS 15 to 209~GB in macOS 26. Do note Apple Intelligence has not been installed on either.
7. Quick Look preview is laggy. It feels as if it's dropping frames, like its 20 fps. I have filed a feedback for this.
8. My browser of choice- Firefox, hasn't been updated for Liquid Glass. This is obviously not on Apple.
9. Contacts has lag when resizing it's window.

Impressions over the next few days:

1. Auto-Brightness can be reset! Turning auto-brightness off and back on resets its behavior to default, just like on iOS. I have wanted this for years. Yay!
2. System responsiveness, animations feel a tinge bit slower. It feels as if actions take 1/5th of a second longer. In the grand scheme of macOS 26, this is very minor.
3. Pop-ups in the system just like Quick Look run at choppy frame rates.
4. Menu Bar items (Status menus) no longer remember their position. For eg- "Now Playing", an item which only appears if there is media playing, moves back to it's original position beside the WiFi icon even if I had manually moved it elsewhere. Menu items, even third-party ones would remember their place in macOS 15. I have made a feedback for this as well.
5. "Battery level" under the Battery section in System Settings is no longer highlighted when the device is plugged. It is used to have this green accent/highlight in macOS 15. Activity Monitor still has the battery status for the past 12 Hours so it's not a huge deal.
6. Battery life is perfectly fine. I didn't notice any change whatsoever.
7. AirPods Pros now have a little "pop-up", dynamic island style when they connect to the Mac. It's cute, I like it.
8. Command+i in Finder which shows the information of the selected file no longer shows the metadata of .MOV files under "More Info". Up until macOS 15 I would use it to copy coordinates, check dates. This is a step back, come on.

The Command+i thing was the straw that broke the camel's back.

So on 9th October I rolled back to 15.7.1. macOS 26, in some ways doesn't have feature parity with macOS 15.

Anyway,

I will update to macOS 26 when they fix these things. I hope the bugs, performance issues, lost features will be fixed/added in the next few months.

And, I look forward to where they take Liquid Glass+Flat design. I am certain it will be better with macOS 27.

Thank you for your kind attention to this matter. Goodbye and god bless Macistan.