At first it was real buggy but since then they've come out with a few cumulative updates that have fixed a lot of the issues. Startup is very quick now, I reach my login screen in about 8 seconds. Start menu has had a complete redesign, your gonna either love it or hate it, at first I wasn't too keen on it but it's growing on me now. Out of sheer habit I still start to drag my cursor over to the left bottom of the screen and then I remember that the start menu is in the center now. This can be changed by the way in the settings and make it appear back on the left. The system tray calendar has had a facelift and looks pretty snazzy, the notifications system has been refined and converged into the calendar pullout. Clicking on the network icon in the systray reveals a totally revamped popup that has airplane mode, focus assist, battery saver, night light and even the sind volume slider. Context menus have been totally redesigned as you can see from the image below and by clicking on Show More Options will bring up the old context menu.
New Context Menu when right clicking an image file.
The New Menu in Explorer has been redesigned and the ribbon has been removed.
View Menu has been redesigned.
Rounded corners have been introduced as well as a cool looking border around the edges of whatever you have open, and the color is dependent on what have chosen as your accent color.
New Start Menu redesigned.
That's just to name a few, there's lots of other cool features, too many to list here. I guess you'll just have to try it to find out.
Of course there will be some people that don't like it and stick with what they have. That's what's neat about the Microsoft Insider Program is you can preview it and you have 15 days to mess around with it and if you don't like it you can easily revert back to Win10 and you don't have to reinstall your apps when installing Win11 or reverting back to Win10. When it's finally released to the general public it'll be a free upgrade to Windows 10 users.