It’s awful. The mobile experience is worse.
If your workgroup/company use Teams/Channels in Teams at all, expect communication to be lost.
It automatically hides Teams that you don’t use often - so if you send alerts to certain Teams or only monitor a team, it requires 4+ clicks per channel to restore. Undoing the combined view does NOT fix this.
It combines chat and teams and moves Teams below Chat by default. If you have many chats, you will be scrolling to find your teams. This is especially bad on laptop screens and unusable on mobile causing a load of scrolling.
This change causes uses confusion further blurring the line between chat and channels, which further causes information sprawl as users struggle to decide to share file via group chat (onedrive) instead of a Team (Sharepoint).
This update is poorly thought out. Admins should have a way to restrict it. Expect major user impact (tickets) when it hits Prod.